abstract
Our results show that areas with high marine biodiversity in the Mediterranean Sea are mainly located along the central and north shores, with lower values in the south-eastern regions. Areas of potential high cumulative threats are widespread in both the western and eastern basins, with fewer areas located in the south-eastern region. The interaction between areas of high biodiversity and threats for invertebrates, fishes and large animals in general (including large fishes, marine mammals, marine turtles and seabirds) is concentrated in the coastal areas of Spain, Gulf of Lions, north-eastern Ligurian Sea, Adriatic Sea, Aegean Sea, south-eastern Turkey and regions surrounding the Nile Delta and north-west African coasts. Areas of concern are larger for marine mammal and seabird species.

abstract
Marine oil spills usually harm organisms at two interfaces, near the water surface and on shore. However, due to the depth of the April 2010 Deepwater Horizon well blowout, deeper parts of the Gulf of Mexico are likely impacted. We estimate the potential negative economic effects of this blow out and oil spill on commercial and recreational fishing, as well as mariculture (marine aquaculture) in the U.S. Gulf area, by computing potential losses throughout the fish value chain. We find that the spill could, in the next seven years, result in (midpoint) present value losses of total revenues, total profits, wages, and economic impact of US$3.7, $1.9, $1.2, and $8.7 billion, respectively. Commercial and recreational fisheries would likely suffer most losses, with an estimated US$1.6 and US$1.9 billion of total revenue loss, US$0.8 and 1.1 billion in total profit, and US$4.9 and US$3.5 billion of total economic impact for commercial and recreational fisheries, respectively.

keywords     Oil spill, marine ecosystems, ecological impact, profit, wages

abstract
The Government of Madagascar plans to increase marine protected area coverage by over one million hectares. To assist this process, we compare four methods for marine spatial planning of Madagascar’s west coast. Input data for each method was drawn from the same variables: fishing pressure, exposure to climate change, and biodiversity (habitats, species distributions, biological richness, and biodiversity value). The first method compares visual color classifications of primary variables, the second uses binary combinations of these variables to produce a categorical classification of management actions, the third is a target-based optimization using Marxan, and the fourth is conservation ranking with Zonation. We present results from each method, and compare the latter three approaches for spatial coverage, biodiversity representation, fishing cost and persistence probability. All results included large areas in the north, central, and southern parts of western Madagascar. Achieving 30% representation targets with Marxan required twice the fish catch loss than the categorical method. The categorical classification and Zonation do not consider targets for conservation features. However, when we reduced Marxan targets to 16.3%, matching the representation level of the “strict protection” class of the categorical result, the methods show similar catch losses. The management category portfolio has complete coverage, and presents several management recommendations including strict protection. Zonation produces rapid conservation rankings across large, diverse datasets. Marxan is useful for identifying strict protected areas that meet representation targets, and minimize exposure probabilities for conservation features at low economic cost. We show that methods based on Zonation and a simple combination of variables can produce results comparable to Marxan for species representation and catch losses, demonstrating the value of comparing alternative approaches during initial stages of the planning process. Choosing an appropriate approach ultimately depends on scientific and political factors including representation targets, likelihood of adoption, and persistence goals.

abstract
Up to one-third of commercial fishery stocks maybe overfished at present. By analyzing catch trends and applying an empirical relationship derived from stock assessments, this article tracks the geographic spread of overfishing at the country level in terms of lost catch and lost revenue, from the start of industrialized fishing in 1950–2004The results tell a cautionary tale of serial depletion to meet the ever-rising demand for fish. Examining country losses with respect to fishery management reveals that overcapacity and excess fishing effort are widespread, but also that recent trends towards sustainability can stabilize or reverse losses(e.g. for Norway, Iceland, the US, Canada, Australia, and New Zealand). Global trade effectively masks the successive depletion of stocks, so that without decisive action to reduce fishing effort, many more stocks will suffer and undernourishment impacts for the major exporting, food-deficit nations will only magnify.

keywords     Overfishing,Fisheries management, depletion, sustainability

abstract
In recent decades, invertebrate fisheries have expanded in catch and value worldwide. One increasingly harvested group is sea cucumbers (class Holothuroidea), which are highly valued in Asia and sold as trepang or beˆche-de-mer. We compiled global landings, economic data, and country-specific assessment and management reports to synthesize global trends in sea cucumber fisheries, evaluate potential drivers, and test for local and global serial exploitation patterns. Although some sea cucumber fisheries have existed for centuries, catch trends of most individual fisheries followed boom-and-bust patterns since the 1950s, declining nearly as quickly as they expanded. New fisheries expanded five to six times faster in 1990 compared to 1960 and at an increasing distance from Asia, encompassing a global fishery by the 1990s. Global sea cucumber production was correlated to the Japanese yen at a leading lag. Regional assessments revealed that population declines from overfishing occurred in 81% of sea cucumber fisheries, average harvested body size declined in 35%, harvesters moved from near- to off-shore regions in 51% and from high- to low-value species in 76%. Thirty-eight per cent of sea cucumber fisheries remained unregulated, and illegal catches were of concern in half. Our results suggest that development patterns of sea cucumber fisheries are largely predictable, often unsustainable and frequently too rapid for effective management responses. We discuss potential ecosystem and human community consequences and urge for better monitoring and reporting of catch and abundance, proper scientific stock assessment and consideration of international trade regulations to ensure long-term and sustainable harvesting of sea cucumbers worldwide.

keywords     Beche-de-mer, echinoderms, global market, invertebrate fisheries,, global fisheries

abstract
Worldwide, finfish fisheries are receiving increasing assessment and regulation, slowly leading to more sustainable exploitation and rebuilding. In their wake, invertebrate fisheries are rapidly expanding with little scientific scrutiny despite increasing socio-economic importance.

keywords     invertebrate, fisheries, global, ecosystem

abstract
According to a recent World Bank report, the intensification of global fishing effort and the ensuing depletion of marine fish stocks causes economic losses of 50 billion US dollars annually. Data deficiencies, however, currently hamper analysis of global fishing effort. We analyzed data from the Food and Agricultural Organization of the United Nations (FAO), the EUROPA fishing fleet registry, and peer-reviewed and other publications, to determine the global trends in fishing effort from 1950 to 2006. Our results show that global fishing effort, expressed as total engine power and the number of fishing days in a year (kilowatt · days), was roughly constant from 1950 to 1970, and then steadily increased up to the present. Europe dominated global fishing effort, followed by Asia. Projecting current trends suggests that Asia will soon surpass Europe. Trawlers contribute a major fraction of global fishing effort, as do vessels greater than 100 gross registered tons. Current estimates of global fishing effort, the number of vessels, and total vessel tonnage are, however, underestimates given the data gaps that we have identified. Our results are useful in the following ways: (1) they encourage researchers in academia and government to improve global fishing effort databases; (2) they allow deeper global analyses of the impact of fishing on marine ecosystems; (3) they induce caution in accepting current underestimates of economic losses of global fisheries; and (4) they reinforce calls for a reduction in global fishing effort.

keywords     fishing effort, global fishing, databases

abstract
We present here the first standardized data on the global distribution, abundance, population trends, and impact of major threats for all known species of scombrids and billfishes [see supporting online material (SOM) for details].

keywords     tuna, billfish, threat, global

abstract
The development of a new global database of fishing cost is described, and an overview of fishing cost patterns at national, regional, and global scales is provided. This fishing cost database provides economic information required for assessing the economics of fisheries at various scales. It covers variable and fixed costs of maritime countries, representing 98% of global landings in 2005. Linked to country and gear-type combinations, cost estimates can be mapped to a database of spatially allocated fisheries catches for future analysis in both spatial and temporal dimensions. The global average variable cost per tonne of catch in 2005 is estimated to range between US$639 and $1217, and the total cost per tonne from $763 to $1477, with mean values of $928 and $1120, respectively. The total global variable fishing cost is estimated to be in the range US$50–96 billion per year, with a mean of $73 billion per annum in 2005 dollar equivalents.

keywords     catches, database, fisheries, fishing cost, fixed cost, fuel cost, global cost, sustainability, variable cost

abstract
The Mediterranean Sea (0.82% of the global oceanic surface) holds 4%–18% of all known marine species (w17,000), with a high proportion of endemism [1, 2]. This exceptional biodiversity is under severe threats [1] but benefits from a system of 100 marine protected areas (MPAs). Surprisingly, the spatial congruence of fish biodiversity hot spots with this MPA system and the areas of high fishing pressure has not been assessed. Moreover, evolutionary and functional breadth of species assemblages [3] has been largely overlooked in marine systems. Here we adopted a multifaceted approach to biodiversity by considering the species richness of total, endemic, and threatened coastal fish assemblages as well as their functional and phylogenetic diversity. We show that these fish biodiversity components are spatially mismatched. The MPA system covers a small surface of the Mediterranean (0.4%) and is spatially congruent with the hot spots of all taxonomic components of fish diversity. However, it misses hot spots of functional and phylogenetic diversity. In addition, hot spots of endemic species richness and phylogenetic diversity are spatially congruent with hot spots of fishery impact. Our results highlight that future conservation strategies and assessment efficiency of current reserve systems will need to be revisited after deconstructing the different components of biodiversity.

keywords     Mediterranean, biodiversity, hot spots

abstract
As coastal fisheries around the world have collapsed, industrial fishing has spread seaward and deeper in pursuit of the last economically attractive concentrations of fishable biomass. For a seafood-hungry world depending on the oceans’ ecosystem services, it is crucial to know whether deep-sea fisheries can be sustainable. The deepsea is by far the largest but least productive part of the oceans, although in very limited places fish biomass can be very high. Most deep-sea fishes have life histories giving them far less population resilience/productivity than shallow-water fishes, and could be fished sustainably only at very low catch rates if population resilience were the sole consideration. But like old-growth trees and great whales, their biomass makes them tempting targets while their low productivity creates strong economic incentive to liquidate their populations rather than exploiting them sustainably (Clark’sLaw). Many deep-sea fisheries use bottom trawls, which often have high impacts on nontarget fishes (e.g., sharks) and invertebrates (e.g.,corals), and can often proceed only because they receive massive government subsidies. The combination of very low target population productivity, nonselectivefishing gear, economics that favor population liquidation and a very weak regulatory regime makes deep-sea fisheries unsustainable with very few exceptions. Rather, deep-sea fisheries more closely resemble mining operations that serially eliminate fishable populations and moveon. Instead of mining fish from the least-suitable places on Earth, an ecologically and economically preferable strategy would be rebuilding and sustainably fishing resilient populations in the most suitable places, namely shallower and more productive marine ecosystems that are closer to markets.

keywords     Sustainability, deep-sea fisheries, fisheries collapse, fisheries economics, high seas, global fisheries

abstract
Given the economic and social importance of fisheries in the Gulf of Mexico large marine ecosystem (LME), it is imperative to quantify the potential impacts of the Deepwater Horizon oil spill. To provide a preliminary perspective of the consequences of this disaster, spatial databases of annual reported commercial catch and landed value prior to the spill were investigated relative to the location of the fisheries closures during July 2010. Recent trends illustrated by this study suggest that more than 20% of the average annual U.S. commercial catch in the Gulf has been affected by postspill fisheries closures, indicating a potential minimum loss in annual landed value of US$247 million. Lucrative shrimp, blue crab, menhaden, and oyster fisheries may be at greatest risk of economic losses. Overall, it is evident that the oil spill has impacted a highly productive area of crucial economic significance within the Gulf of Mexico LME. This study draws attention to the need for ongoing and thorough investigations into the economic impacts of the oil spill on Gulf fisheries.

keywords     oil spill, Gulf of Mexico, shrimp, closures

abstract
Marine fisheries have endured for centuries but the last 50 years have seen a drastic increase in their reach and intensity. We generate global estimates of biomass for marine ecosystems and evaluate the effects that fisheries have had on ocean biomass since the 1950s. A simple but versatile ecosystem model was used to represent ecosystems as a function of energy fluxes through trophic levels. Using primary production data, sea surface temperature, transfer efficiency, fisheries catch and trophic level of species, the model was applied on a half-degree spatial grid covering all oceans. Estimates of biomass by trophic levels were derived for marine ecosystems in an unexploited state, as well as for all decades since the 1950s. Trends in the decline of marine biomass from the unexploited state were analyzed with a special emphasis on predator species since they are highly vulnerable to overexploitation. This study highlights three main trends about the global effects of fishing: (1) predators are more affected than organisms at lower trophic levels; (2) declines in ecosystem biomass are stronger along coastlines than in the High Seas; (3) the extent of fishing and its impacts have expanded from north temperate to equatorial and southern waters in the last 50 years. More specfically, this modelling work shows that many oceans historically exploited by humans have seen a drastic decline in their predator biomass, with about half of the coastal areas of the North Atlantic and North Pacific showing a decline in predator biomass of more than 90%.

keywords     ecosystem modelling, biomass, fisheries, marine predators, trophic level, global

abstract
Fourteen indicators of marine living resource management performance by country, reflecting both their intention to sustainably use the resource within their Exclusive Economic Zones and the effectiveness of their policies, were developed and the performances of 53 maritime countries were assessed. Four rankings of the countries, which jointly account for over 95 percent of the world’s marine fisheries landings, are presented here as aggregated scores of the fourteen indicators, using differentschemes for weighting the indicators, each reflective of the management preferences identified by the Global Environment Outlook 4 (GEO4) future development scenarios: Market First; Policy First; Security First; and Sustainability First. The resulting rankings differed substantially between the weighting schemes for the top performing countries but less so for the countries performing poorly.

keywords     Environmental indicator, fisheries sustainability, mariculture, marine mammal, seabird

abstract
Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management. The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders. This indicator underpins reported trends in human impacts, declining when predators collapse (“fishing down marine food webs”) and when low-trophic-level fisheries expand (“fishing through marine food webs”). The assumption is that catch MTL measures changes in ecosystem MTL and biodiversity. Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments and find that catch MTL does not reliably predict changes in marine ecosystems. Instead, catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL, we observe recent increases in catch, survey and assessment MTL. However, catches from most trophic levels are rising, which can intensify fishery collapses even when MTL trends are stable or increasing. To detect fishing impacts on marine biodiversity, we recommend greater efforts to measure true abundance trends for marine species, especially those most vulnerable to fishing.

keywords     Marine Trophic Index, global marine, catch, ecosystems

abstract
Climate change is altering the rate and distribution of primary productivity in the world’s oceans. Predicting effects of changes in primary production on marine ecosystems and fisheries will assist the conservation of marine biodiversity and the sustainable management of fisheries. However, predicting the response of populations to primary production change is difficult, because inter-specific interactions can influence outcomes. We simulated the effects of change in primary production on Australian marine ecosystems across a wide latitudinal range using the marine food web model called ‘Ecosim’. We link models of primary production under climate change with Ecosim to predict changes in fishery catch, fishery value, abundance of animals of conservation interest, and indicators of community composition. Under a plausible climate change scenario, primary production will increase around Australia and generally this benefits fisheries catch and value and abundance of threatened marine animals such as turtles and sharks, but surprisingly, community composition was not strongly affected. However, ecological interactions reverse the expected responses for some populations, resulting in loss of value for some specific fisheries and localised declines for two threatened marine animal populations. We conclude that climate-driven primary production change should be considered by marine ecosystem managers and production increases can simultaneously benefit fisheries and conservation of biodiversity. Greater focus on incorporating biological interactions into management will significantly improve the ability to identify species and industries most at risk from climate change.

keywords     climate change, marine, ecosystem modelling, Ecopath

abstract
In 2002, world leaders committed through the Convention on Biological Diversity (CBD) to achieve a significant reduction in the rate of biodiversity loss by 2010. We compiled 31 indicators to report on progress toward this target. Most indicators of the state of biodiversity (covering species’ population trends, extinction risk, habitat extent/condition, and community composition) showed declines, with no significant recent reductions inrate, whereas indicators of pressures on biodiversity (including resource consumption, invasive alien species, nitrogen pollution, over-exploitation, and climate change impacts) showed increases. Despite some local successes and increasing responses (including extent and biodiversity coverage of protected areas, sustainable forest management, policy responses to invasive alien species, and biodiversity-related aid), the rate of biodiversity loss does not appear to be slowing.

keywords     global, biodiversity, marine

abstract
Primary production must constrain the amount of fish and invertebrates available to expanding fisheries; however the degree of limitation has only been demonstrated at regional scales to date. Here we show that phytoplanktonic primary production, estimated from an ocean-color satellite (SeaWiFS), is related to global fisheries catches at the scale of Large Marine Ecosystems, while accounting for temperature and ecological factors such as ecosystem size and type, species richness, animal body size, and the degree and nature of fisheries exploitation. Indeed we show that global fisheries catch since 1950 have been increasingly constrained by the amount of primary production. The primary production appropriated by current global fisheries is 17 to 112% higher than that appropriated by sustainable fisheries. Global primary production appears to be declining, in some part due to climate variability and change, with consequences for the near future fisheries catches.

keywords     Fisheries,Bottom-up, Large Marine Ecosystem, quantile regression, transfer efficiency

abstract
Previous projection of climate change impacts on global food supply focuses solely on production from terrestrial biomes, ignoring the large contribution of animal protein from marine capture fisheries. Here, we project changes in global catch potential for 1,066 species of exploited marine fish and invertebrates from 2005 to 2055 under climate change scenarios. We show that climate change may lead to large scale re-distribution of global catch potential, with an average of 30 - 70% increase in high latitude regions and a drop of up to 40% in the tropics. Moreover, maximum catch potential declines considerably in the southward margins of semi-enclosed seas while it increases in poleward tips of continental shelf margins. Such changes are most apparent in the Pacific Ocean. Among the 20 most important fishing Exclusive Economic Zone (EEZ) regions in terms of their total landings, EEZ regions with the highest increase in catch potential by 2055 include Norway, Greenland, US (Alaska) and Russia (Asia). On the contrary, EEZ regions with the biggest loss in maximum catch potential include Indonesia, USA (excluding Alaska and Hawaii), Chile, and China. Many highly impacted regions, particularly those in the tropics, are socio-economically vulnerable to these changes. 36 Thus, our results indicate the need to develop adaptation policy that could minimize climate change impacts through fisheries. The study also provides information which may be useful to evaluate fisheries management options under climate change.

keywords     Climate change, global, marine, fisheries, catch, redistribution

abstract
Cephalopods are a key component of marine food webs, providing sustenance for myriad marine species. Cephalopods are also of increasing economic importance as evidenced by the rapid rise in their global landings over recent decades. If fisheries continue on this trajectory, conflicts may transpire among cephalopod and finfish fisheries, particularly in ecosystems where cephalopods are highly valuable both directly as a landed commodity and indirectly as prey for other harvested species. We provide the first measure of the ecosystem services that cephalopods contribute to fisheries in 28 marine ecosystems, both as a commodity and an ecological support service. We also evaluate how current demands on cephalopods compare to mid-20th century conditions. We find that cephalopod contributions to fisheries vary widely, but are substantial in many ecosystems. Commodity and supportive services provided by cephalopods contributed as much as 55% of fishery landings (tonnes) and 70% of landed values ($USD). The contribution of cephalopods as a commodity was generally greatest in the coastal ecosystems, whereas their contribution as a supportive service was highest in open ocean systems. Further, the commodity and supportive services provided by cephalopods to fisheries landings increased in most of the coastal ecosystems between the mid-20th century (years 1960–70) and contemporary periods (years 1990–2004), indicating the rising demand for cephalopods. Current demands have no historical precedent and ecosystems in which cephalopods are highly exploited as a targeted resource and as an ecological support service should be further evaluated to prevent the unsustainable development of marine fisheries within them.

keywords     cephalopod, global, marine, fisheries

abstract
Today, seamount fish populations are in trouble following a 30-year history of overexploitation, depletion, and collapse, with untold consequences for global biodiversity and the complex, delicate, but poorly understood, open-ocean food webs. Seamount fishes are especially vulnerable to fishing because their “boomand-bust” life history characteristics can be exploited by heavy, high-technology fisheries. We estimate present global seamount catches to be about 3 million tonnes per annum and increasing—vastly in excess of estimated sustainable levels. Unfortunately, most seamount fisheries are unmanaged. In a few developed countries, precautionary management regimes have recently been introduced, including protection from bottom trawling. Small-scale artisanal fisheries using less-harmful fishing gear, patial closures, and low catch levels provide an attractive model for improved seamount fishery management that could foster the reconstruction of previously damaged seamount ecosystems. Such restored systems might one day support a substantial global sustainable fishery, although, like many other fisheries, the prognosis is poor.

keywords     seamount, fisheries, trawling

abstract
Successful ocean management need consider not only fishing impacts, but drivers of harvest. Consolidating post-1950 global catch and economic data, we assess which attributes of fisheries are good indicators for fishery development. Surprisingly, year of development and economic value are not correlated with fishery trophic levels. Instead, patterns emerge of profit-driven fishing for attributes related to costs and revenues. Fisheries initially developed on shallow ranging species with large catch, high price, and big body size, and then expanded to less desirable species. Revenues expected from developed fisheries declined 95% during 1951-1999, and few high catch or valuable fishing opportunities remain. These results highlight the importance of economic attributes of species as leading indicators for harvest-related impacts in ocean ecosystems.

keywords     fishing, harvest, management, business, trophic level

abstract
Excess fishing capacity and the growth in global demand for fishery products have made overfishing ubiquitous in the world’s oceans. Here we describe the potential catch losses due to unsustainable fishing in all countries’ exclusive economic zones (EEZs) and on the high seas over 1950-2004. To do so, we relied upon catch and price statistics from the Sea Around Us Project as well as an empirical relationship we derived from species stock assessments by the U.S. National Oceanic and Atmospheric Administration. In 2000 alone, estimated global catch losses amounted to 7-36% of the actual tonnage landed that year, resulting in a landed value loss of between $6.4 and 36 billion (in 2004 constant US$). From 1950-2004, 36-53% of commercial species in 55-66% of EEZs may have been overfished. Referring to a species-level database of intrinsic vulnerability (V) based on life-history traits, it appears that susceptible species were depleted quickly and serially, with the average V of potential catch losses declining at a similar rate to that of actual landings. The three continental regions to incur greatest losses by mass were Europe, North America, and Asia—forming a geographic progression in time. But low-income and small island nations, heavily dependent on marine resources for protein, were impacted most profoundly. Our analysis shows that without the inexorable march of overfishing, ~20 million people worldwide could have averted undernourishment in 2000. For the same year, total catch in the waters of low-income food deficit nations might have been up to 17% greater than the tonnage actually landed there. The situation may be worst for Africa, which in our analysis registered losses of about 9-49% of its actual catches by mass in year 2000, thus seriously threatening progress towards the UN Millennium Development Goals.

keywords     value loss, protein, nourishment, global

abstract
Using a recently developed database of fisheries subsidies for 148 maritime countries spanning 1989 to the present, total fisheries subsidies for the year 2003 is computed. A key feature of our estimation approach is that it explicitly deals with missing data from official sources, and includes estimates of subsidies to developing country fisheries. Our analysis suggests that global fisheries subsidies for 2003 are between US$ 25 and 29 billion, which is higher than an earlier World Bank estimate of between US$ 14–20 billion. This new estimate is lower than our 2000 global subsidies estimate of US$ 30–34 billion.We find that fuel subsidies compose about 15–30% of total global fishing subsidies, and that capacity enhancing subsidies sum to US$ 16 billion or about 60% of the total. These results imply that the global community is paying.

keywords     subsidies, global fisheries, value

abstract
The life spans of demersal species of fishes occurring in deepwaters are much longer and their potential growth rates much lower than those of related shallow water species. As a result, deep-sea demersal fish species are more vulnerable to exploitation. This is because low growth rates relative to the available market discount rate for capital makes it desirable for fishing firms to mine, rather than sustainably exploit, these resources even in the absence of fisheries subsidies. However, it is common knowledge that governments around the world do provide subsidies to their fishing industries. The objective of this contribution is to estimate the global amount of subsidies paid to bottom trawl fleets operating in the highseas, i.e., outside of the Exclusive Economic Zones of maritime countries. Our study suggests that fisheries subsidies to these fleets stand at about US$ 152million per year, which constitutes 25%of the total landed value of the fleet. Economic data for bottom trawlers suggest that the profit achieved by this vessel group is normally not more than 10%of landed value. The implication of this finding is that without subsidies, the bulk of the world’s bottom trawl fleet operating in the high seas will be operating at a loss, and unable to fish, thereby reducing the current threat to deep-sea and high seas fish stocks.

keywords     Fisheries subsidies, High seas, deep-sea fisheries, sustainability

abstract
Using estimates of the primary production required (PPR) to support fisheries catches (a measure of the footprint of fishing), we analyzed the geographical expansion of the global marine fisheries from 1950 to 2005. We used multiple threshold levels of PPR as percentage of local primary production to define 'fisheries exploitation' and applied them to the global dataset of spatially-explicit marine fisheries catches. This approach enabled us to assign exploitation status across a 0.5 latitude/longitude ocean grid system and trace the change in their status over the 56-year time period. This result highlights the global scale expansion in marine fisheries, from the coastal waters off North Atlantic and West Pacific to the waters in the Southern Hemisphere and into the high seas. The southward expansion of fisheries occurred at a rate of almost one degree latitude per year, with the greatest period of expansion occurring in the 1980s and early 1990s. By the mid 1990s, a third of the world's ocean, and two-third of continental shelves, were exploited at a level where PPR of fisheries exceed 10% of PP, leaving only unproductive waters of high seas, and relatively inaccessible waters in the Arctic and Antarctic as the last remaining 'frontiers.' The growth in marine fisheries catches for more than half a century was only made possible through exploitation of new fishing grounds. Their rapidly diminishing number indicates a global limit to growth and highlights the urgent need for a transition to sustainable fishing through reduction of PPR.

keywords     global fisheries, marine fisheries; primary production; sustainability; human footprint

abstract
This paper describes the marine fish and invertebrate consumption in three of the world’s major seafood markets (the EU, Japan and the USA)using a series of global maps indicating the likely origin of the seafood consumed by each market. These maps display a high level of dependence by these markets on foreign sources as the serial depletion of local fisheries resources forced the fleets in search for new seafood supplies well beyond their domestic waters. The acquisition of foreign(and highseas) seafood by these markets is conducted through two channels: by dispatching distant water fishing fleets that directly exploit foreign stocks; and by importing catch landed elsewhere by local fleets. The results also demonstrate that each of the three major markets occupies a zone of influence within which it is dominant.

keywords     Seafood consumption; global fisheries; international trade; sustainability

abstract
Illegal and unreported fishing contributes to overexploitation of fish stocks and is a hindrance to the recovery of fish populations and ecosystems. This study is the first to undertake a world-wide analysis of illegal and unreported fishing. Reviewing the situation in 54 countries and on the high seas, we estimate that lower and upper estimates of the total value of current illegal and unreported fishing losses worldwide are between $10bn and $23.5bn annually, representing between 11 and 26 million tonnes. Our data are of sufficient resolution to detect regional differences in the level and trend of illegal fishing over the last 20 years, and we can report a significant correlation between governance and the level of illegal fishing. Developing countries are most at risk from illegal fishing, with total estimated catches in West Africa being 40% higher than reported catches. Such levels of exploitation severely hamper the sustainable management of marine ecosystems. Although there have been some successes in reducing the level of illegal fishing in some areas, these developments are relatively recent and follow growing international focus on the problem. This paper provides the baseline against which successful action to curb illegal fishing can be judged.

keywords     Illegal catch, IUU, global catch

abstract
Climate change can impact the pattern of marine biodiversity through changes in species’ distributions. However, global studies on climate change impacts on ocean biodiversity have not been performed so far. Our paper aims to investigate the global patterns of such impacts by projecting the distributional ranges of a sample of 1066 exploited marine fish and invertebrates for 2050 using a newly developed dynamic bioclimate envelope model. Our projections show that climate change may lead to numerous local extinction in the sub-polar regions, the tropics and semi-enclosed seas. Simultaneously, species invasion is projected to be most intense in the Arctic and the Southern Ocean. Together, they result in dramatic species turnovers of over 60% of the present biodiversity, implying ecological disturbances that potentially disrupt ecosystem services. Our projections can be viewed as a set of hypothesis for future analytical and empirical studies.

keywords     Bioclimate envelope, climate change impact, global marine biodiversity, niche-based model, species turnover

abstract
We present a newmethodology for database-driven ecosystem model generation and apply the methodology to theworld’s 66 currently defined Large Marine Ecosystems. Themethod relies on a largenumber of spatial and temporal databases, including FishBase, SeaLifeBase, as well as several other databases developed notably as part of the Sea Around Us project. The models are formulated using the freely available Ecopath with Ecosim (EwE) modeling approach and software. We tune the models by fitting to available time series data, but recognize that the models represent only a first-generation of database-driven ecosystem models.We use the models to obtain a first estimate of fish biomass in the world’s LMEs. The biggest hurdles at present to further model development and validation are insufficient time series trend information, and data on spatial fishing effort.

keywords     Ecopath with Ecosim, Ecosytem model, global model, LME, biomass

abstract
Ongoing declines in production of the world’s fisheries may have serious ecological and socioeconomic consequences. As a result, a number of international efforts have sought to improve management and prevent overexploitation, while helping to maintain biodiversity and a sustainable food supply. Although these initiatives have received broad acceptance, the extent to which corrective measures have been implemented and are effective remains largely unknown. We used a survey approach, validated with empirical data, and enquiries to over 13,000 fisheries experts to assess the current effectiveness of fisheries management regimes worldwide; for each of those regimes we also calculated the probable sustainability of reported catches to determine how management affects fisheries sustainability. Our survey shows that 7% of all coastal states undergo rigorous scientific assessment for the generation of management policies, 1.4% also have a participatory and transparent processes to convert scientific recommendations into policy and 0.95% also provide for robust mechanisms to ensure the compliance with regulations; none is also free of the effects of excess fishing capacity, subsidies or access to foreign fishing. A comparison of 2 fisheries management attributes with the sustainability of reported fisheries catches indicated that the conversion of scientific advice into policy, through a participatory and transparent process, is at the core of achieving fisheries sustainability, regardless of other attributes of the fisheries. Our results illustrate the great vulnerability of the world's fisheries and the urgent need to meet wellidentified guidelines for sustainable management; they also provide a baseline against which future changes can be quantified.

keywords     fisheries, global, management, sustainability

abstract
After a long history of overexploitation, increasing efforts to restore marine ecosystems and rebuild fisheries are under way. Here, we analyze current trends from a fisheries and conservation perspective. In 5 of 10 well-studied ecosystems, the average exploitation rate has recently declined and is now at or below the rate predicted to achieve maximum sustainable yield for seven systems. Yet 63% of assessed fish stocks worldwide still require rebuilding, and even lower exploitation rates are needed to reverse the collapse of vulnerable species. Combined fisheries and conservation objectives can be achieved by merging diverse management actions, including catch restrictions, gear modification, and closed areas, depending on local context. Impacts of international fleets and the lack of alternatives to fishing complicate prospects for rebuilding fisheries in many poorer regions, highlighting the need for a global perspective on rebuilding marine resources.

keywords     fisheries, global, management, recovery, collapse

abstract
Global changes are shaping the life history and biogeography of marine species, which then affects their fisheries. Macroecology theories, which deal with large scale relationships between life history and biogeography, can be used to develop models to predict effects of global changes on marine species and hence on their fisheries. Firstly, based on theories of allometric scaling of metabolism and trophic energetic, we develop a theoretical model that relates maximum catch potential from a species with its trophic level, geographic range, mean primary production within the species’ range, and the fraction that is exploited at the geographic range. Secondly, using this theoretical model and data from 1,000 species of exploited marine fishes and invertebrates, we analyze the empirical relationship between species’ approximated maximum catch potential, their life history, and biogeography variables. The empirical model has high explanatory power and agrees with expectations from theory. Although problems in the original data and the imprecision of model parameters result in high variance between the empirical model and the data, predictions of relative changes in catch potential under climate change-induced changes in biogeography should be robust to uncertainties. In the future, this empirical model can be combined with bioclimate envelope model to predict the socio-economic impacts of climate change on marine fisheries, and this is illustrated here with an example pertaining to the small yellow croaker (Larimichthys polyactis, Sciaendae) from the East China Sea.

keywords     global warming, climate change, global fisheries, macroecology, geographic range

abstract
Conservation prioritization and management of the oceans require spatially explicit information on how all types of human activities impact marine ecosystems, but methods for globally assessing such impacts and mapping their distribution have not previously existed. Using a novel ecosystem-specific and scale-independent model, we synthesized 17 global datasets on anthropogenic threats to 20 marine ecosystems. Results show that every part of the oceans is affected by humans and that a large fraction (34%) is heavily impacted, including both nearshore and offshore ecosystems in nearly every corner of the world. Although human impact on marine ecosystems is pervasive, areas of little impact remain, particularly near the poles. Our quantitative approach provides important guidelines for where conservation action and threat mitigation are most needed for achieving global management and conservation goals.

keywords     mapping, global marine ecosystems, human threats, impacts

abstract
The distribution of pelagic marine fishes and invertebrates varies seasonally. However, information on the seasonal variation of the distribution of most pelagic marine fishes and invertebrates is scarce. In this paper, seasonal changes in distribution ranges of commercially exploited pelagic fishes and invertebrates are predicted based on the existing Sea Around Us Project distribution, a prediction algorithm, the correlation between seasonal hanges in northsouth boundaries and sea surface temperature. In the northern hemisphere, in summer (July to September), mobile pelagic marine species tend to migrate to the northern part of their distribution range to avoid excessive temperature near the equator, while in winter (January to March), the same species will migrate southward to avoid the low temperature at higher latitudes. The converse applies to the southern hemisphere. The resulting distributions can improve the prediction of temperature preference profile of pelagic species which are important in evaluating the effects of global warming on their distribution ranges. However, this method of predicting summer and winter distributions of pelagic species can only be considered as an approximation as other factors such as food availability, salinity, rainfall and current are not included. On the other hand, such approximation appear reasonable, given the global scope of the application of the predicted seasonal distributions and the large number of evaluated species (> 16o).

keywords     modelling, seasonal, distribution, pelagic, marine fishes, squids

abstract
The distribution ranges of organisms, and marine animals in particular, are a manifestation of their environmental requirements, although they are often modified by the dynamics of prey and predators. Distribution range maps can also be used to infer where an activity occurs which requires the presence of a set of species, e.g., a fishery which targets them. The distribution of marine fishes and invertebrates serves as the basis for the mapping of fisheries by the Sea Around Us Project. Thus, accurate range maps are extremely important, and an earlier contribution by Close et al. (2006; FCRR 14(4): 27-37) reviews the step-by-step approach, and the assumptions used to predict the distribution of relative abundance of marine fishes and invertebrates from broad geographical limits, e.g., ocean basins, latitudinal limits, depth limits, etc., to relatively narrow polygons surrounding a number of ½ degree lat.-long. cells. Once established, such distributions, at least those referring to demersal fishes and invertebrates, can be interfaced with a map of sea bottom temperature, and inferred temperature preference profiles (TPP). These can be used, among other things, to verify the distribution ranges as predicted distributions should generate unimodal TPP, with the bulk of the distributions spanning a narrow range of temperature (~100 Celsius). As a relatively large fraction of the TPP that we obtained at first appeared bimodal, or exhibited a strong kurtosis, the assumption was revisited that the distribution of a species with regard to latitude can be simulated by an equal-sided triangle. It is shown here, for the cod (Gadus morhua), and generally for all our over 900 demersal species, that assuming a skewed triangular distribution, whose degree of skew is proportional to the temperature gradient from low to high latitude, generates more realistic distributions when compared to observed species distribution maps, although the narrowing of the uni-modal temperature probability distributions is relatively small. This correction will be implemented in all distribution ranges of demersal fishes and invertebrates in the Sea Around Us database, and used for catch allocation, and inferences on climate shifted distributions due to climate change.

keywords     distribution, marine fishes, invertebrates

abstract
As human impacts to the environment accelerate, disparities in the distribution of damages between rich and poor nations mount. Globally, environmental change is dramatically affecting the flow of ecosystem services, but the distribution of ecological damages and their driving forces have not been estimated previously. Here we give conservative, considerably partial estimates of the environmental costs of human activities over 1961-2000 in six major categories: climate change, stratospheric ozone depletion, agricultural intensification and expansion, deforestation, overfishing, and mangrove conversion. We calculate total costs ranging up to $47 trillion (net present value, 2005 international $), 92% of the year 2000 world GDP, purchasing power parity-adjusted. By quantitatively connecting the costs borne by rich, middle-income, and poor nations to activities by the three groups, we find striking imbalances. Up to 87% of the impacts of climate change and ozone depletion that are predicted to be borne by low-income nations have been directly driven by emissions from the middle- and high-income groups. Indeed, due to rich countries’ disproportionate emissions of greenhouse gases, poor nations may bear climate impacts 68% more than their year 2000 foreign debt. In a world increasingly connected ecologically and economically, our analysis is an early step towards reframing issues of development, globalization, and international debt in accordance with true ecological costs.

keywords     Global impacts, debt, biological impacts, over-fishing

abstract
Global fisheries are currently overcapitalized, resulting in overfishing in many of the world’s fisheries. Given that fuel constitutes a significant component of fishing costs, we expect recent increases in fuel prices to reduce overcapacity and overfishing. However, government fuel subsidies to the fishing sector reduce, if not completely negate, this positive aspect of increasing fuel costs. Here, we explore the theoretical basis for the expectation that the increasing fuel prices faced by fishing enterprises will reduce fishing pressure. Next, we estimate the amount of fuel subsidies to the fishing sector by governments globally to be in the range of US$4.2–8.5 billion per year. Hence, depending on how much of this subsidy existed before the recent fuel price increases, fishing enterprises, as a group, can absorb as much as this amount of increase in their fuel budget before any conservation benefits occur as a result of fuel price increases.

keywords     subsidy, global fishing, fuel, price

abstract
We identify marine fishes most vulnerable to exploitation in different environments by comparing life history traits, represented by an index of intrinsic vulnerability. We then evaluate global changes in the mean vulnerability of catches comprising different species assemblages. Over the past 50 years, declines in mean vulnerability reveal increasing domination by low intrinsic vulnerability species. Coral reef fishes show the strongest decline, followed by seamount and estuarine assemblages: declines are most likely a result of rapid over-exploitation of highly vulnerable species. This is supported by a correlation between the spatial distributions of fishes listed under the IUCN Red List of Threatened Species and the rates of decline of mean vulnerability of catches. Fishes on the Red List are generally highly vulnerable. Deep water demersal and benthopelagic fishes, particularly those aggregated around seamounts, also have higher intrinsic vulnerability. These findings suggest that coral reef and seamount ecosystems potentially suffer high conservation risks from fishing. Moreover, concentrations of threatened fishes and strong declines in the mean vulnerability of catches in the Indo-Pacific and Caribbean highlight these regions for conservation attention.

keywords     global catch vulnerability

abstract
Coexistence of foraging seabirds and operating fisheries may result in interactions such as competition for the same prey resources. We used GIS-based modelling at a scale of 30-min spatial cells to: (a) map the foraging distribution of seabirds; (b) predict their annual food consumption rates in a spatially-explicit manner; and (c) estimate a spatially-explicit seabird – fisheries overlap index. Information on population size, diet composition, and foraging attributes of 351 seabird species was compiled into a Microsoft Access database. Global annual food consumption by seabirds was estimated to be 96.4 million tonnes (95% CI: 78.0 to 114.7 million tonnes), compared to a total catch of nearly 120 million tonnes by all marine fisheries. Krill and cephalopods comprised over 58% of the overall food consumed and fishes most of the remainder. The families Procellariidae (albatrosses, petrels, shearwaters, etc.) and Spheniscidae (penguins) were responsible for over 54% of the overall food consumption. Seabird foraging distribution maps revealed that areas around New Zealand, the eastern Australian coast, and the sub-Antarctic islands had high species richness. However, temperate and polar regions supported high seabird densities, and most food extracted by seabirds originated there. Furthermore, maps of food consumption rates revealed that most food consumed by seabirds was extracted from offshore rather than nearshore waters, and from areas where seabird – fisheries overlap was low. The resource overlap maps identified ‘hotspots’ of highest potential for conflict between fisheries and seabirds. Thus, this study may provide useful insight when developing management approaches for designing offshore marine conservation areas.

keywords     seabird – fisheries interactions, resource overlap, foraging distribution, seabird food consumption

abstract
The World Trade Organization (WTO) is in a unique position to move global fisheries towards sustainability. The current Doha Trade Round of Negotiations offers an important opportunity to improve the future prospects of fish as a main source of animal protein for one fifth of the world’s population. Countries are wrestling with the issue of government fisheries subsidies, which keep too many commercial fishing boats in operation and drive the unsustainable exploitation of the world’s depleted fish populations. Removal of subsidies is challenging as it cannot be resolved without international cooperation because unilateral action has trade implications, and may not work because fish and fishing vessels do not respect national exclusive economic zones. This is why the WTO, which has in place mechanisms to enforce its agreements, is the only institution that can tackle the global problem of overfishing subsidies. We identify the opportunities and challenges that WTO members face, and provide suggestions on how to address these challenges.

keywords     subsidy, global fisheries, WTO

abstract
We describe the first effort at creating a global ex-vessel fish price database, which is required for understanding the economic behaviour of participants in the world’s fisheries. We demonstrate potential applications of the database by linking it to a spatially defined catch database, which makes it possible to attach landed values to species in both time and space. This is the first database available publicly where interested members of the public, researchers and managers can easily find and access ex-vessel prices of the world’s major commercial fish species. Preliminary results indicate that the average real price of a number of species have declined between 1950 and 2002. The estimated landed value of fish globally, in year 2000 dollars, was about US$24 billion in 1950. It increased steadily to about US$90 billion in the early 1970s, reached a peak of US$100 billion at the end of the 1980s, and declined to about US$80 billion in 2000. The top 15 fishing countries cumulatively account for 79% of total real landed value, with Japan leading, even though the value of its landings has been declining.

keywords     landed values, catches, spatial mappting and temporal applications

abstract
The issue of conservation and sustainable use of high seas resources is increasingly becoming significant, as is reflected in the number of planned international activities in ocean science and management, e.g. the United Nations General Assembly Working Group on marine biodiversity beyond national jurisdiction. Essentially, the increasing exploitation pressure on high and deep sea resources makes discussion of viable policy options for international waters an important topic. To our knowledge, this paper provides the first global, economically supported assessment of the impact on fisheries of potentially protecting a portion of the high seas in no-take marine protected areas. Such closures are likely to result in relatively little global annual profit loss. For example, closure of 20% of the high seas may lead to the loss of only 1.8% of the current global reported marine fisheries catch, and a decrease in profits to the high seas fleet of about US$270 million per year. Thus, at globally minimal costs, the international community could benefit substantially by securing insurance against extinctions and the loss of the spectacular marine diversity in the high and deep seas, while protecting many market and non-market values for the benefit of both current and future generations.

keywords     marine protected area, MPA, high seas, global , marine reserve

abstract
Distribution ranges of commercial fish and invertebrates are required by the Sea Around Us Project for mapping of global fisheries catches. However, published ranges exist for only a small fraction of the 1231 taxa, composed of 923 species, 161 genera and 147 higher groups used in the latest version of the mapping process (Version 3.1, representative of catches from 1950 to 2003). This paper summarizes the methods employed by the Sea Around Us Project to reduce potentially global distributions to realistic ranges by identifying key ecological information for each of the 1231 commercial taxa, specifically: (i) presence in FAO area(s); (ii) latitudinal range; (iii) range-limiting polygons; (iv) depth range; and (v) habitat preferences. Furthermore, this paper presents an additional filter that outlines how (ii) and (iv) are used to correct the depth range for the effect of ‘equatorial submergence.’ Several examples are used to illustrate this process, notably the Florida pompano (Trachinotus carolinus) and the Silver hake (Merluccius bilinearis). Throughout this paper, the data sources emphasized include FishBase, other fish and invertebrate databases, and online information where applicable. In addition, simple heuristics are used to replace ecological information that is unavailable or missing. It should be noted that the Sea Around Us Project does not explicitly use temperature and primary production for any of the procedures discussed in this paper. The purpose of this is to allow for subsequent analyses of distribution ranges using these variables.

keywords     range, distribution, commerical fishes, commerical invertebrates, global

abstract
This contribution presents estimates of the amounts and distributions of small pelagic fishes (i.e., ‘forage fish’) consumed by the 115 species of marine mammals and the 351 species of seabirds known to feed in the world’s marine waters. The methods used for mapping the distribution of these predators and of their prey, detailed elsewhere, are briefly recalled. Marine mammals, in the 1990s, annually consumed about 20.2 million t of small pelagics, or roughly 12 % of their food consumption; for seabirds, the corresponding figures, also applying to the 1990s, are 12.1 million t of small pelagics and 12.5 % of their food consumption. Overall, we find that marine mammals and seabirds do not compromise human exploitation of small pelagics. On the other hand, reduced biomasses of small pelagics are a challenge for numerous species of marine mammals and seabirds.

keywords     Fishmeal, Forage fish, marine mammals, seabirds

abstract
We developed a large-scale habitat suitability modeling approach to map global distributions of 115 species of marine mammals. Predictions were generated by first assigning each species to broad-scale categories of habitat preferences with respect to depth, sea surface temperature and ice edge association based on synopses of published qualitative and quantitative habitat preference information. Using a global grid with 0.5 degree lat/long cell dimensions, we generated an index of the relative environmental suitability (RES) of each cell for a given species by relating quantified habitat preferences to locally averaged environmental conditions in a GIS modeling framework. RES predictions closely matched published maximum range extents for most species, suggesting that our model-based approach for identifying habitat represents a useful, more objective alternative to existing sketched distributional outlines. In addition, raster-based predictions provided more detailed information about heterogeneous patterns of potentially suitable habitat for species throughout their range. We validated RES model outputs for eleven species (northern fur seal, harbor porpoise, sperm whale, killer whale, hourglass dolphin, fin whale, humpback whale, blue whale and Antarctic minke whale) from a broad taxonomic and geographic range using at-sea sightings from dedicated surveys. Observed relative encounter rates and species-specific predicted environmental suitability were significantly and positively correlated for all, but one species. In comparison, observed encounter rates were correlated with < 1 % of 1000 simulated random data sets for all but two species. Mapping of suitable habitat for marine mammals using this environmental envelope model is helpful for evaluating current assumptions and knowledge about species? occurrences, especially for data-poor species. Moreover, RES modeling may help to focus research efforts on smaller geographic scales and usefully supplement other, statistical, habitat suitability models.

keywords     spatial modeling;habitat prediction;RES;habitat suitability

abstract
Fishery subsidies greatly impact the sustainability of fishery resources. Subsidies that reduce the cost of fisheries operations and those that enhance revenues make fishing enterprises more profitable than they would be otherwise. Such subsidies result in fishery resources being overexploited, as they contribute directly or indirectly to the build-up of excessive fishing capacity, thereby undermining the sustainability of marine living resources and the livelihoods that depend on them. In this contribution, fishery subsidies are identified and categorized, taking into onsideration the policy relevance of fishery subsidies worldwide, subsidy program descriptions, sources of funding, scope and coverage, annual total amounts, administering authority, and the recipients of the subsidy. Using this taxonomy, a database of subsidy programs reported in marine capture fisheries for 144 coastal countries was compiled spanning 1995 to 2005. From this, an annual estimate of subsidies paid to the fishing sector by governments globally is computed for 2000. This static estimate accounts explicitly for data gaps. Total global fishery subsidies were estimated at about US$26 billion for the eleven subsidy types identified in this study (excluding fuel subsidies). About 60% of this amount was provided by 38 developed countries and the remaining 40% by 103 developing countries. The proportion of estimated subsidies that contributed towards an increase in fishing capacity globally amounted to about US$15 billion, while subsidies that contributed to fisheries management and conservation programs were approximately US$7 billion. The remaining US$4 billion are defined as ugly subsidies, i.e., they may lead either to fisheries conservation or to overcapacity depending on the context. Japan and the EU were the highest subsidizers of their fisheries, with about US$4.2 billion and US$3.0 billion, respectively. The results from this study have policy implications for fisheries subsidy reforms at the on-going WTO negotiations on rules to eliminate subsidies that cause overcapacity, and in achieving sustainable fisheries management. In conclusion, three major areas are highlighted for future research, the impact of subsidies on: (i) resource exploitation, (ii) industrial profits, and (iii) food sufficiency and livelihoods.

keywords     subsidy, forage fish,

abstract
Global landings of demersal marine fishes are demonstrated to have shifted to deeper water species over the last 50 years. Our analysis suggests deep-water fish stocks may be at serious risk of depletion, as their life histories render them highly vulnerable to overfishing with little resilience to over-exploitation. Deep-sea fisheries are exploiting the last refuges for commercial fish species and should not be seen as a eplacement for declining resources in shallower waters. Instead, deep-water habitats are new candidates for conservation.

keywords     deep-sea, deep-water fisheries, fisheries crisis, global trends, global

abstract
The life spans of demersal species of fishes occurring in deep waters are much longer and their potential growth rates much lower than those of related shallow water species. As a result, deep-sea demersal fish species are more vulnerable to exploitation. This is because low growth rates relative to the available market discount rate for capital makes it desirable for fishing firms to mine, rather than sustainably exploit, these resources even in the absence of fisheries subsidies. However, it is common knowledge that governments around the world do provide subsidies to their fishing industries. The objective of this contribution is to estimate the global amount of subsidies paid to bottom trawl fleets operating in the high seas, i.e., outside of the Exclusive Economic Zones of maritime countries. Our study suggests that fisheries subsidies to these fleets stand at about US$152 million per year, which constitutes 15% of the total landed value of the fleet. Economic data for bottom trawlers suggest that the profit achieved by this vessel group is normally not more than 10% of landed value. The implication of this finding is that without subsidies, the bulk of the world’s bottom trawl fleet operating in the high seas will be operating at a loss, and unable to fish, thereby reducing the current threat to deep-sea and high seas fish stocks.

keywords     subsidy, bottow trawl, global, high seas

abstract
It is generally accepted that global fisheries are grossly overcapitalized, resulting in overfishing in most of the world’s fisheries. Fuel prices have recently seen significant increases. Given that fuel constitutes a significant component of fishing costs, it is obvious that, other things being equal, increasing fuel prices will reduce overcapacity and overfishing, because they will reduce the profits that can be made, thereby driving marginal fishers out of fishing. But, other things are hardly equal. Here, the willingness of governments to provide the fishing sector fuel subsidies reduce, if not completely negate, the conservation value of increasing fuel costs. The objective of this contribution is twofold. First, we explore the theoretical basis for the expectation that increasing fuel price faced by fishing enterprises will, everything being equal, reduce fishing pressure. Second, we estimate the amount of fuel subsidies (defined narrowly here as the price differential between what others and fishers pay in an economy) paid to the fishing sector by governments globally. Results from our study indicate that global fuel subsidies stand at between US$ 6±2 billion per year. This implies that, depending on how much of this subsidy existed before the fuel price increase, fishing enterprises can, in the aggregate, absorb as much as this amount of increase in their fuel budget before we begin to see any conservation benefits from fuel price increases.

keywords     subsidy, forage fish, fuel, global

abstract
Following a brief historical review of the emergence of fisheries for forage fish that are primarily destined for reduction, and their competition with fisheries for human consumption, an account is given of landing trends in various parts of the world, and catch maps are provided for the 1970s and 2000s which allow spatial and temporal comparisons. A brief account is also given of the changing species composition of the landings, the exploitation status of the fisheries, the trophic levels trends of species destined for reduction, the fuel consumption of the global fleet exploiting forage fish which are primarily small pelagics, the fishing gear they use, and the ex-vessel prices they fetch.

keywords     fishmeal, forage fish, global fisheries

abstract
Fishing gears, instrumental to the fishing process, can exert direct impacts on marine communities and habitats. The database described here allows for the analysis of global fishing patterns, by associating all reported global catch with fishing gear types. The fine spatial detail of the Sea Around Us project?s catch database allows for the construction of maps showing subtle changes in the use of fishing gears annually since 1950. Maps included in this report chronicle the expansion of these and other gears in ways that will inform the current debate over their impacts, and provide critical information to shape policy development and management choices.

keywords     fishing gear, database, catch, trawl, dredge, purse seine

abstract
Fishing gears, instrumental to the fishing process, exert direct but often poorly documented impacts on marine communities and habitats. Analysis of global fishing patterns is now possible using a database that associates all global catch with fishing gear types. Maps prepared from this database are particularly useful to help assess the impact of fishing gears such as bottom trawls and dredges, which have been shown to have significant impacts on marine communities.

keywords     fishing gear, database, catch, trawl, dredge

abstract
Human-dominated marine ecosystems are experiencing accelerating loss of populations and species, with largely unknown consequences. We analyzed local experiments, longterm regional time series, and global fisheries data to test how biodiversity loss affects marine ecosystem services across temporal and spatial scales. Overall, rates of resource collapse increased, and recovery potential, stability, and water quality decreased exponentially with declining diversity. Restoration of iodiversity, in contrast, increased productivity four-fold and decreased variability by 21%, on average. We conclude that marine biodiversity loss is increasingly impairing the ocean's capacity to provide food, maintain water quality, and recover from perturbations. Yet, available data suggest that at this point these trends are still reversible.

keywords     marine biodiversity, value biodiversity, services, global

abstract
Maps of the species richness in the high seas are presented, which are based on the distribution of individual species of marine invertebrate and vertebrate groups, complemented with maps of genera and families of invertebrates and fishes. High seas refers to marine areas outside the 200-mile exclusive economic zones (EEZs) and continental shelf areas, or other described national jurisdictions.We considered known latitudinal and longitudinal gradients of the distribution of species richness (declining from the equator, and from a global center of species richness about Indonesia) where appropriate. Maps of the known locations of cold-water corals and seamounts are also presented. There is suggestive evidence that cold-water coral are associated with seamounts. If validated, this would allow predicting the existence of far more cold-water corals sites than so far documented. Both habitat types are threatened by trawling. Lastly, a map of the distribution of threatened non-fish vertebrates is provided. Together, these maps indicate marine biodiversity in the high seas to be richly patterned, with some of these patterns helping to identify areas in need of protection such as seamounts, and the high seas of the Southwest Pacific.

keywords     biodiversity, distribution, global, high seas

abstract
We estimate biomass trends for demersal and large pelagic fishes, (i.e., excluding small pelagic and mesopelagic fishes) based on 17 Ecopath models from Mauritania, Cape Verde, Senegal, the Gambia, Guinea, and Guinea-Bissau, Sierra Leone and the open waters of the central east Atlantic, made to represent various time periods during the second half of the 20th Century. We use a published method developed for estimating fish biomass in the North Atlantic, and modify it to account for the specificity of West African fisheries and ecosystems. We show that, overall, fish biomass as defined here (i.e., excluding low-trophic level and small fishes) has declined over the forty year period from 1960 by a factor of 13. An implication of our results is that further increase in fishing mortality in the region will not lead to increased catches but will only drive biomasses further down. The economic and political consequences of our findings are briefly discussed.

abstract
Characterized by over-exploitation of many of the commercial stocks, the fisheries of the world are in a crisis. In particular, pressure is extremely strong on predators at the top of marine food webs. Typically, the fisheries for these predators, once initiated, last about 10-15 years, i.e., from the time the fisheries start developing and catches are minimal to the time catches have peaked, and then collapsed. This is particularly true for elasmobranchs (mainly sharks, rays and skates), which are characterized by high longevity and low fecundity. Among the elasmobranchs, large rays are particularly susceptible to trawl fishing, although in most countries, they are not targeted, but form part of the by-catch. In fact, one of the first documented extirpations (i.e., local extinctions) of marine fish was of a ray in the Irish Sea. As a large long-lived elasmobranch, the Cowtail stingray (Pastinachus sephen) is extremely susceptible to overfishing, and is widely caught as by-catch of the shrimp trawl fisheries throughout its Indo-Pacific range. The development of targeted fisheries for this stingray, driven by the luxury leather market demand for its skin for processing into pens, wallets, boots, etc., will accelerate the depletion to which this and allied species are already subjected. None of the countries in which the Cowtail stingray is abundant have fisheries management systems in place for this or any other species of rays. It can be expected that the directed fisheries will expand geographically from their center in Southeast Asia, as the original stocks are depleted (as has been the case for fisheries elsewhere), leaving devastated stocks behind. The fisheries science community has no way of ensuring that this exploitation can be made sustainable. It is questionable, therefore, that a demand for luxury products should be allowed to expand that may devastate this and related species, and the ecosystems of which they are a part.

keywords     rays, fisheries, global, stingray

abstract
Since the demonstration, in 1998, of the phenomenon now widely known as ?fishing down marine food webs?, and the publication of a critical rejoinder by FAO staff, a number of studies have been conducted in different parts of the world, based on more detailed data than the global FAO fisheries statistics originally used, which established the validity and ubiquity of this phenomenon. In this contribution, we briefly review how, rather than being an artifact of biased data, this phenomenon was in fact largely masked by such data, and is, indeed, more widespread than was initially anticipated. This is here made visible by comparing two global maps of trophic level (TL) changes from the early 1950s to the present. The first presents the 50 year difference of the grand mean TL values originally used to demonstrate the fishing down effect, while the second is based on means above a cutoff TL (here set at 3.25), thus eliminating the highly variable and abundant small pelagic fishes caught throughout the world. Based on this, we suggest that using mean TL as ?Marine Trophic Index? (MTI), as endorsed by the Convention on Biological Diversity always be done with an explicitly stated cutoff TL (i.e., cutMTI), chosen (as is the case with our proposed value of 3.25) such as to emphasize changes in the relative abundance of the more threatened, high-TL fishes. We also point out the need to improve the taxonomic resolution, completeness and accuracy of the national and international fisheries catch data series upon which the cutMTI is to be based.

keywords     global trophic biodiversity measure

abstract
This contribution, which reviews broad trends in the history of fisheries, argues that sustainability, however defined, rarely if ever occurred as a result of an explicit policy, but as result of our inability to access a major part of exploited stocks. With the development of industrial fishing, and the resulting invasion of the refuges previously provided by distance and depth, our interactions with fisheries resources have come to resemble the wars of extermination that newly arrived hunters conducted 40-50,00 years ago in Australia, and 11-12,000 years ago against large terrestrial mammals. These broad trends are documented here through maps of change in trophic levels and fish sizes, which displays characteristic declines, first in the nearshore waters of industrialized countries of the Northern Hemisphere, then spread offshore and to the Southern Hemisphere. This geographical extension met its natural limit in the late 1980s, when the catches from newly accessed stocks ceased to compensate for the collapsed in areas accessed earlier, hence leading to a gradual decline of global landing. These trends affect developing countries stronger than the developed world, which have been able to meet the shortfall by increasing imports from developing countries. These trends, however, along with the rapid growth of farming of carnivorous fish, which consumes other fish suited for human consumption, has led to serious food security issue. This gives urgency to the implementation of the remedies traditionally proposed to alleviate overfishing (reduction of overcapacity, enforcement of conservative TACs, etc.), and to the implementation of non-conventional approaches, notably the re-establishment of the refuges (a.k.a. marine reserve), which made possible the apparent sustainability of pre-industrial fisheries.

keywords     global trends world fisheries marine food security

abstract
Marine fisheries are the most diverse of the major global food-producing sectors, both in terms of their outputs (species landed1) and the technology used2. One characteristic, however, common to nearly all contemporary fisheries is their dependence on fossil fuels. While numerous analyses have been undertaken to quantify fuel inputs to a wide range of fisheries3,4,5,6,7,8, to date, no attempt has been made to determine the fossil fuel consumption of the world's fishing fleets. Here, we calculate that for 2000, they burned approximately 56.7 billion litres of fuel in the process of landing just over 85 million tonnes of marine fish and invertebrates. Consequently, contemporary fisheries yield approximately 1.77 tonnes of fish per tonne of fuel burned. Moreover, total fuel inputs to the world's fishing fleets account for about 1.4% of total global oil consumption.

keywords     fuel, energy, global fleets

abstract
A new approach is presented which allows broad regional landing statistics from FAO and other sources to be examined as detailed catch maps using avail-able knowledge of the distribution of commercial species and historical records of fishing access arrangements. Results are presented as time series composi-tions and as regional maps detailing changes since 1950 to 2000. These catches can be related to current exclusive economic zone boundaries and to the areas represented by ecological models (such as Ecospace), facilitating better use of landing statistics in economic, ecological and other analysis.

keywords     global mapping

abstract
Globally, the most basic need of policy makers and fisheries managers is to know what catch was taken within their jurisdictional boundaries, and which countries took it. Surprisingly, for many countries this has not been possible. We introduce a web site devoted to making this and related information available to everyone via the internet.

keywords     internet, catch, global

abstract
A bioeconomic model was developed to evaluate the potential performance of brown tiger prawn stock enhancement in Exmouth Gulf, Australia. This paper presents the framework for the bioeconomic model and risk assessment for all components of a stock enhancement operation, i.e. hatchery, grow-out, releasing, population dynamics, fishery, and monitoring, for a commercial scale enhancement of about 100 metric tonnes, a 25% increase in average annual catch in Exmouth Gulf. The model incorporates uncertainty in estimates of parameters by using a distribution for the parameter over a certain range, based on experiments, published data, or similar studies. Monte Carlo simulation was then used to quantify the effects of these uncertainties on the model-output and on the economic potential of a particular production target. The model incorporates density-dependent effects in the nursery grounds of brown tiger prawns. The results predict that a release of 21 million 1 g prawns would produce an estimated enhanced prawn catch of about 100 t. This scale of enhancement has a 66.5% chance of making a profit. The largest contributor to the overall uncertainty of the enhanced prawn catch was the post-release mortality, followed by the densitydependent mortality caused by released prawns. These two mortality rates are most difficult to estimate in practice and are much under-researched in stock enhancement.

keywords     Bioeconomic modelling; Risk assessment; Stock enhancement; Tiger prawn; Penaeus esculentus

abstract
Examination of the effects of fishing on marine ecosystems requires historical catch data on appropriate spatial scales. Most commercial fishing data are currently only available in the form of landings data that do not delineate the marine area from which the catch was extracted. Even when statistics are available by defined spatial areas rather than by port landings, such as the statistical areas used by the Food and Agriculture Organization (FAO) of the United Nations, these reporting areas are often much larger in extent than the areas defined as ecosystems by most current ecological models and are difficult to use without modification. A rule-based spatial allocation procedure was employed using a Microsoft Visual Basic application called ?SimMap? that has the ability to create and decompose ArcView shapefiles. An ESRI plug-in (Map Objects Lite) was used to provide the ability to show shapefiles created dynamically as a result of the catch allocation process. By creating Access databases describing the distribution of some 1 500 commercial fisheries taxa, as well as the plethora of fishing access arrangements nations have with other nations, we were able to create procedures for spatially allocating broader fisheries catch statistics into a global system of 30-minute latitude by 30-minute longitude spatial cells. This paper presents the FAO catch data allocated to our global system of spatial cells for the year 2000. This sample output is indicative of the results achievable through the SimMap program which has previously been used to demonstrate the impacts of fishing on the marine ecosystems of the North and South Atlantic, including biomass and trophic levels, to calculate direct overlaps of fisheries with populations of marine mammals, and to illustrate the spatial distributions of catch values and energy consumption by fishing fleets. Using the SimMap program, anomalies in official fisheries landings reported by countries to the FAO have been detected and have led to revised global statistics and historical trajectories.

keywords     mapping landings saup

abstract
Fishing gears, instrumental to the fishing process, exert direct but often poorly documented impacts on marine communities and habitats. A database is described here that associates all global catch with fishing gear types allowing for the analysis of global fishing patterns. The fine spatial detail of the Sea Around Us project?s catch database allows for the construction of maps showing subtle changes in the use of fishing gears annually since 1950. These maps are particularly useful to help assess the impact of fishing gears such as bottom trawls and dredges, which have been shown to have significant impacts on marine communities. Maps included in this report chronicle the expansion of these and other gears in ways that will inform debate over their impacts, and proved critical information to inform policy development and management choices

keywords     global,fishing gear,trawl

abstract
Mapping global landings is an important prerequisite for examining causal relationships between fishing and ecological change. Landing statistics, typically provided with poor spatial precision, can be disaggregated into a grid system of spatialcells (30 min x 30 min) using a rule-based approach and ancillary data about distributions of fished taxa and fishing access of reporting countries. Presentation of time series catch composition is then possible for many types of marine areas including biogeochemical provinces, large marine ecosystems and exclusive economic zones.

keywords     fisheries landings, fisheries statistics, global fisheries, mapping

abstract
Serious stock depletion on continental shelves helped create new pressure for alternative fishing grounds. In particular, seamounts were among those ?newly? targeted ecosystems that have been intensively fished since the second half of the 20th century. But what are the seamount fisheries? How have their catches changed in recent years? Can we map where these catches are taken? This paper describes the progress of this work. Most seamount species are also found on the continental slope, making the allocation of reported catches to specific seamounts difficult. Thus, future mapping of landings will require species distributions that allow proportioning of catches between slope areas and those taken on seamounts. Catches of fishes identified as mostly occurring on seamounts only began in 1967, initially with the Orange roughy fishery. The catches of these species have only continued because new seamounts with harvestable stocks were discovered as fisheries collapsed, and because new stocks or species were targeted. A pattern of successive rapid development and decline is evident. While the percent of fisheries that collapsed is somewhat similar for seamount species and those not associated with seamounts, it is obvious that those fisheries that are based on species found only on seamounts have collapsed with greater frequency and had poorer recovery. This points towards the conclusion that not only seamount fisheries, but deep-water trawling in general, may not be sustainable in the long term.

keywords     seamount,fisheries

abstract
We estimate the biomass of high-trophic level fishes in the North Atlantic at a spatial scale of 0.5º latitude by 0.5º longitude based on 23 spatialized ecosystem models, each constructed to represent a given year or short period from 1880 to 1998. We extract over 7 800 data points that describe the abundance of high-trophic level fishes as a function of year, primary production, depth, temperature, latitude, ice cover and catch composition. We then use a multiple linear regression to predict the spatial abundance for all North Atlantic spatial cells for 1900 and for each year from 1950 to 1999. The results indicate that the biomass of high-trophic level fishes has declined by two-thirds during the last 50-year period, and with a factor of nine over the century. Catches of high-trophic level fishes increased from 2.4 to 4.7 million tonnes annually in the late 1960s, and subsequently declined to below 2 million tonnes annually in the late 1990s. The fishing intensity for high-trophic level fishes tripled during the first half of the time period and remained high during the last half of the time period. Comparing the fishing intensity to similar measures from 35 assessments of high-trophic level fish populations from the North Atlantic, we conclude that the trends in the two data series are similar. Our results raise serious concern for the future of the North Atlantic as a diverse, healthy ecosystem; we may soon be left with only low-trophic level species in the sea.

keywords     ecopath, saup, biomass decline, ecosystem modelling, north atlantic, predatory fish

abstract
The delineation of geographic ranges for cryptic marine mammal species is often subjective and limited to roughly sketched outlines encompassing all known records. We developed a new, more quantitative approach to map the distribution of marine species based on existing knowledge about habitat preferences and demonstrate this approach on beaked whales (Ziphiidae, Cetacea), one of the least known families of mammals. We used available published information about species-specific habitat preferences with respect to depth, sea surface temperature and ice-edge association to assign species to broad-scale, quantified habitat categories. Using a raster-based GIS model, we related the quantified preferences to locally averaged oceanographic conditions. Predicted distributions closely matched published information about maximum range extents for most species, encompassing at least 90 % of all known sighting records. In addition, raster-based predictions provided more detailed information about the relative suitability of the environment for a species throughout its range. To test the validity of the approach, we developed a simulation model of ziphiid strandings using a global data set of residual ocean currents. Relative probabilities of strandings were generated based on two different input distributions: species-specific habitat suitability predictions and a uniform distribution based on published information. Simulated strandings based on habitat suitability predictions produced significant correlations with observed strandings for more than twice as many species (11 of 21 ziphiid species) as those generated based on uniform distributions (5/21). Thus, results provided support for our quantitative approach to map species distributions. The visualization of potentially important habitat areas based on this GIS approach will help to re-evaluate current assumptions and knowledge about marine mammal distribution. This in turn will help focus research efforts in the context of the impact of underwater noise pollution on ziphiids and other management issues.

abstract
Formal analyses of long- term global marine fisheries prospects have yet to be performed, as fisheries research focuses on local, species-specific management issues. Extrapolation of present trends implies expansion of bottom fisheries into deeper waters, serious impact on biodiversity, and declining global catches, the last possibly aggravated by fuel cost increases. Examination of four scenarios, covering various societal development choices suggests that the negative trends now besetting fisheries can be turned around, and their supporting ecosystems rebuilt, at least partly.

keywords     global; biodiversity; catch scenario; energy; fuel

abstract
Formal analyses of long- term global marine fisheries prospects have yet to be performed, as fisheries research focuses on local, species-specific management issues. Extrapolation of present trends implies expansion of bottom fisheries into deeper waters, serious impact on biodiversity, and declining global catches, the last possibly aggravated by fuel cost increases. Examination of four scenarios, covering various societal development choices suggests that the negative trends now besetting fisheries can be turned around, and their supporting ecosystems rebuilt, at least partly.

keywords     global; biodiversity; catch scenario; energy; fuel

abstract
Overfishing has slashed stock - especially of large predator species - to an all-time low worldwide, according to new data. If we don't manage this resource, we will be left with a diet of jellyfish and plankton stew.

keywords     global; landings; saup

abstract
Meeting the widely expressed requirement that fisheries should somehow be managed on an ?ecosystem basis? implies that fisheries-relevant ecological processes, and the fisheries themselves, need to be documented in the form of maps. This allows recovery, in intuitive fashion, of at least some of the many dimensions of the complex ecosystems in which the fisheries are embedded. The implied transition, in fisheries science, from bivariate time series, to maps as major heuristic devices has a number of implications ? some obvious, some less so ? of which a number are here discussed and illustrated.Amongthe issues covered are: (i) the requirement for a consensus taxonomy of large marine ecosystems; (ii) the need to construct fisheries catch maps in the absence of positive records of what was caught where; (iii) the proper identification of one?s audience; and (iv) the mapping of marine protected areas and reserves. The seriousness of the fisheries crisis is emphasized, and the case is made that fisheries, if ever they are going to achieve some measure of sustainability ? however defined ? ultimately will have to be limited not only through the amount of effort they can effectively deploy, but also limited in space, leading to a change to the defaults under which fisheries operate, currently set such that all aquatic wildlife can be exploited, if under some restrictions.

keywords     ecology; mapping; saup

abstract
Successful placement of protected areas not only relies on a myriad of local social factors relating to current ?resource? users and jurisdictional boundaries, but also on the relevant scale spatial distribution and movement of species, ecosystems and habitats for which protection is sought. Equitable protection can be viewed as a problem with many spatial scales, and conventionally for some there has been little data available. A data mapping process (SimMap) was developed to support a large study on the effect of fishing on marine ecosystems (?The Sea Around Us? project; http://saup.fisheries.ubc.ca) and provides critical data at a number of scales, linking fine-scale ecosystem models (EcoPath/EcoSim/EcoSpace) in a nested fashion to whole ocean basin, and even global distributions of taxa and oceanographic processes. This system supports the spatial ecosystem modelling used to evaluate the impacts of protected areas, and also allows work within these ecosystems to be extrapolated over larger areas and the investigation of temporal changes.

keywords     mpa mapping saup

abstract
The Large Marine Ecosystems (LMEs) of the world annually produce 95% of usable global marine biomass. LMEs are presently being subjected to stresses from unsustainable fishing, climate change, coastal eutrophication, toxic algal blooms and degradation of critical habitats, resulting in significant losses of socioeconomic benefits to coastal countries. The volume provides assessments of the changing states of selected polar, temperate and tropical LMEs using the case study method. From the studies of changes in biomass yields and environmental health, new insights are provided on the causes of the changes and actions presently underway to improve the health and sustainability of LMEs. Twelfth in the series on LMEs (see http://www.lme.noaa.gov), this book is essential reading for scientists and students in marine relevant fields, conservationists, marine resource managers, policy makers and others interested in the fate of ocean ecosystems.

keywords     Large marine ecosystems; global

abstract
In physics, when scientists reach the limit of their instruments? resolution and encounter phenomena that are lurred,they build a bigger machine, a bigger microscope, telescope, or particle detector capable of clearly detecting the phenomena under discussion. The health of our global fisheries is like that ?blurry? phenomenon. In the Sea Around Us Project (initiated and funded by the Pew Charitable Trusts), what we have done is build a bigger machine?one covering not a single bay or gulf but the world?s oceans. This approach is new even though the data we used are not. We used huge amounts of existing data collected by colleagues in government, industry, and academia. They cover not one fish species but all species, especially ?table fish,? those we like to eat. The project encompasses not 3 or 5 years of hard-to-interpret, fluctuating abundances but rather 50 or even 100 years, thus forcing us to confront long-term impacts and trends. For two centuries, we have been dissecting nature into ever-smaller pieces. Now, it is necessary to reassemble the pieces into the larger picture.

keywords     global landings biomass ecology

abstract
Estimation of total harvests of marine organisms is essential if true impacts of fisheries are to be evaluated. Such estimates are difficult to obtain because, for many of the world's fisheries, an unknown proportion of the catch is not reported. Components of the unreported catch may include discards, deliberately misreported catch and unmandated catch (catch that it is not required to be reported). For many fisheries, estimates of misreporting or discarding exist, but may not apply to all periods of interest. Here we demonstrate a methodology for estimating unreported catches over time, based on knowledge of factors that influence misreporting in the fishery and on independent (published and unpublished) estimates of misreporting. Independent estimates and knowledge of influence factors are combined to assign quantitative estimates of misreporting to different periods so that time-series of misreporting can be obtained. The method is demonstrated for two national fisheries: Iceland and Morocco. The Icelandic analysis is a by-species approach for cod and haddock. The Moroccan analysis divides catches into demersal and pelagic categories, rather than individual species. Preliminary results suggest that Icelandic cod catches may have been underestimated by between 1% and 14% at different times, and haddock catches by between 1% and 28%. Underestimation of Moroccan catches appears to have been by as much as half in some cases. Uncertainty has been incorporated into our analyses by using multiple sources of information to provide upper and lower estimates of misreporting and by using a Monte Carlo simulation. These case studies show that it is possible to obtain some estimate of misreporting, even when rigorous data are lacking. Sources of information are presented so that areas where information is lacking are easily identified, offering a basis for comment, discussion and, it is hoped, collaboration that will lead to provision of further information and improvement of the estimates.

keywords     bycatch saup IUU

abstract
Fisheries have rarely been ?sustainable?. Rather, fishing has induced serial depletions, long masked by improved technology, geographic expansion and exploitation of previously spurned species lower in the food web. With global catches declining since the late 1980s, continuation of present trends will lead to supply shortfall, for which aquaculture cannot be expected to compensate, and may well exacerbate. Reducing fishing capacity to appropriate levels will require strong reductions of subsidies. Zoning the oceans into unfished marine reserves and areas with limited levels of fishing effort would allow sustainable fisheries, based on resources embedded in functional, diverse ecosystems.

abstract
La peche industrielle epuise les mers. A l'echelle de la planete, les prises diminuent parce que les populations ne se renouvellent plus. Face a cette evolution preoccupante, une idee gag ne du terrain: constituer de veritables reserves marines dans des zones de plusieurs dizaines de milliers de kiometres carres.

keywords     mpa; biomass; saup

abstract
To evaluate the impacts of fishing on marine ecosystems, the total extraction of fish must be known. Putting a figure on total extraction entails the difficult task of estimating, in addition to reported landings, discards, illegal and unmandated catches. Unreported catches cast various types of shadow, which may be tracked and estimated quantitatively. Some shadows of unreported catches are reviewed, for example, an innovative, well-funded NGO publicizes illegal catch inthe Southern Ocean. For various reasons, official figures often have the implicit but unacceptable assumption that such categories are null.We present an estimation procedure based on adjustment factors taken from observer reports, correspondents and published information that track changes in a regulatory regime, and hence reflect incentives and disincentives to misreport. Monte Carlo simulations address uncertainty using multiple sources of information to provide upper and lower estimates. Once in place, this method provides preliminary estimates that may be refined without disruption. The method is demonstrated for fisheries in Iceland and Morocco. We use a ?by-species? approach for Icelandic cod and haddock, while the Moroccan catch is divided into demersal and pelagic categories. Results suggest that Icelandic cod catches may have been underestimated by between 1 and 14% at different times, and haddock by between 1 and 28%. Underestimation of Moroccan catches appears to have been as much as by 50%. These case studies show that it is possible to obtain estimates of misreporting, even when direct data are lacking. Our method encourages transparency because sources of information are presented so that uncertain values are easily identifed, offering a basis for comment, collaboration and refinement in estimating illegal and unreported fishing.

keywords     bycatch IUU saup

abstract
This contribution briefly describes the major features of the database of fisheries catches from the Eastern USA, from Maine in the North to the tip of the Florida peninsula in the South, i.e., excluding the Gulf of Mexico. The two major databases for commercial and recreational catches created by the National Marine Fisheries Service are described, along with a number of related efforts both at Federal and States? level. Also, some of the scattered contributions devoted to estimating discards, and misreported catches are discussed, with emphasis on their potential by the Sea Around Us project for generating high-resolution catch maps.

keywords     landings; United States; fisheries; saup

abstract
Individual Transferable Quotas (ITQs) are exclusive and transferable rights to harvest a given portion of the total allowable catch of fish. They are one form of 'rights-based management' used to manage the allocation of resources adn interactions between users of marine ecosystems. Fishery managers establish total allowable catch levels (TACs), and divide this among individual fishers or fishing companies in the form of individual harvest quotas, usually a percentage of the TAC. ITQs are transferable by being sold or purchased on the open market. In theory, ITQs can create de facto property rights. The accomplishments and problems of ITQ are discussed.

keywords     conservation marine ITQ quota

abstract
The impact that fishing operations may have on marine mammals and other components of marine ecosystems is a major concern today. Fisheries, in addition to causing by-catch mortalities, affect marine mammals through direct and indirect competition for the same food sources. Our goal was to assess the potential trophic impact of fisheries on mammal populations in the North Atlantic by quantifying the overlap in resource exploitation in space and time using high-resolution modeling and mapping. We developed a relatively simple model to estimate feeding requirements (specified by food type) and population biomass of all North Atlantic marine mammal species. Main model input parameters were population abundance, sex-specific mean body mass, standardized diet compositions, and weight-specific feeding rates. A spatial model was constructed using a geographic information system to link annual food consumption estimates to the corresponding species-specific, rasterized distributional ranges. Spatially explicit food intake (expressed as proportions of total food intake per ½ degree latitude/longitude square) was further refined by incorporating information about habitat preferences and feeding patterns. Superimposing the geographically matching fisheries catches (generated by a similar rule-based model) allowed the calculation of overlap between fisheries catches and marine mammal consumption. The model indicates that, in the North Atlantic, total food consumption of marine mammals in the 1990s was three times higher than total fisheries catches. However, spatially disaggregating consumption and specifying intake by food type showed actual resource overlap to be quite low. Areas of high overlap in the North Atlantic are concentrated along the East coast of North America (35° ? 53° N) and in European shelf waters. This visualization of geographical ?hotspots? of marine mammal-fisheries interactions may help to identify areas of conflict, realized or potential. Hence the meta-analysis approach taken here may serve as a useful management tool in the context of defining marine mammal critical habitat and efficient MPAs design.

keywords     mapping; model; mamma;l fisheries

abstract
Fisheries landing statistics from broad statistical reporting areas were mapped as catches with a resolution of 30 minutes of longitude x 30 minutes of latitude. The procedure involved the progressive disaggregation of the statistics, firstly to provide poorly defined records with a better taxonomic identity, and secondly by using a rule-based process involving databases of known distributions of taxa, oceanographic features and of the areas where reporting countries are permitted to fish, in order to spatially disaggregate the data. Maps prepared for reporting years 1950 until 1999 showed trends in the spatial distribution of fisheries catches, provided a valuable means of examining other questions such as interactions between fishing and marine mammals, and provided descriptions of the global catch from large marine ecosystems. Catch maps prepared for the North Atlantic are illustrated and were used in the formation of ecological models and in the preparation of maps of catch value.

keywords     mapping; landings; saup

abstract
This document presents two interrelated studies on the marine fisheries of the People?s Republic of China, both emphasizing, if in different ways, the magnitude of the catches reported throughout the 1990s. The first study, by Lillian Pang and Daniel Pauly, titled ?Chinese Marine Capture Fisheries from 1950 to the late 1990s: the Hopes, the Plans, and the Data,? reviews the history and development of Chinese marine fisheries since 1950, notably the extremely strong increase of reported catches from the mid-1980s on. The case is then made, based on the design of the statistical reporting system, and the professional motivation structure of local fisheries officials, that over-reporting is likely to be the cause for much of the nominal catch increase. Supporting evidence is provided by similar overreporting in other food-producing sectors, by various other fisheries studies (notably of catch per effort trends), the stressed state of Chinese coastal ecosystems, and the proclamation, by China?s Central Government, of a zero-growth policy designed to undermine local over-reporting and to restructure the fisheries sector. The second study, by Reg Watson, titled ?Spatial Allocation of Fisheries Landings from FAO Statistical Areas 61 and 71? describes a rule-based, computer-intensive algorithm developed by the author and associates to map the world?s fisheries catches in ½ degree cells. The resulting global map, which suggests the Chinese shelf and adjacent waters to be as nearly as productive as the Peruvian coastal upwelling system, was broadly reproduced by a General Additive Model that used depth and primary production as predictor variables. The catches reported from Chinese marine waters explained a large fraction of the differences between observed and predicted values, strongly suggesting that current Chinese nominal catches are greatly over-reported. These two studies thus confirm each other, and provide strong evidence that indeed, Chinese national statistics over-report marine catches from Chinese waters. The internal adjustments that correcting for the underlying deficiency of the statistical reporting system will require are not investigated, and nor are the food policy issues implied by these findings. It is clear, however, that these issues are serious, for both China and the rest of the world, thus explaining, if need be, the critical tone of our studies. It is hoped that the Chinese authorities, international bodies, concerned scientists and others will find harmonious ways to resolve these issues.

keywords     landings; China; saup

abstract
Over 75% of the world marine fisheries catch (over 80 million tonnes per year) is sold on international markets, in contrast to other food commodities (such as rice). At present, only one institution, the Food and Agriculture Organization of the United Nations (FAO) maintains global fisheries statistics. As an intergovernmental organization, however, FAO must generally rely on the statistics provided by member countries, even if it is doubtful that these correspond to reality. Here we show that misreporting by countries with large fisheries, combined with the large and widely fluctuating catch of species such as the Peruvian anchoveta, can cause globally spurious trends. Such trends influence unwise investment decisions by firms in the fishing sector and by banks, and prevent the effective management of international fisheries.

keywords     saup; landings; global; China

abstract
Human's growing appetite for seafood has driven powerful new technologies to find, capture, and transport to market 80 million tons of ocean wildlife each year. Many once common species have been taken in such large numbers that their future commercial value - and their future existence on Earth - may be in jeopardy. This has led to "fishing down the food web" - that is catching species closer to the primary production level that converts sunlight to chlorophyll, the lowest trophic level. This practice could have disastrous effects on the entire ocean biologic system.

abstract
Research on ecosystem-based fisheries management, marine biodiversity conservation, and other fields requires appropriate maps of the major natural regions of the oceans, and their ecosystems. It is proposed here that a classification system proposed by T. Platt and S. Sathyendranath and implemented by A.R. Longhurst, defined largely by physical parameters, and which subdivides the oceans into four ?biomes? and 57 ?biogeochemical provinces? (BGCPs), could be merged with the system of 50 Large Marine Ecosystems (LMEs) identified by K. Sherman and colleagues, which would represent subunits of the provinces. This arrangement enhances each of the systems, and renders them mutually compatible. For the LMEs, subprovinces are pragmatically defined to serve as a framework for the management of coastal fisheries, and other purposes, while the BGCPs have rigorous physical definitions, including borders defined by natural features. Moreover, incorporating the 50 defined LMEs into the framework of BGCPs will allow straightforward scaling-up of LME-specific flow estimates (including fisheries catches) up to basin and ocean scales. The combined mapping will allow the computation of GIS-derived properties such as temperature, primary production, etc., and their analysis in relation to fishery catch data for any study area. A further useful aspect of the proposed scheme is that it will enable us to quantify the EEZ of various countries in terms of the distribution of marine features (e.g., primary production, coral reef areas) which has yet to be traightforwardly aassociated with coastal states. Applications to shelf, coral reef and oceanic fisheries, and to the mapping of marine biodiversity are briefly discussed.

keywords     mapping; global; saup; ecosystem; lme

abstract
We estimate the biomass of high trophic-level fish in the North Atlantic at a spatial scale of 1⁄2 degree latitude by 1⁄2 degree longitude over the time period from 1950 to 1999, based on 23 spatialized, ecosystem models, each constructed to represent a given year or short period from 1880 to 1998. We extract over 7800 data points that describe the abundance of high trophic-level fishes as a function of year, primary production, depth, temperature, latitude, ice cover, and catch composition. We then use a multiple linear regression to predict the spatial abundance for all North Atlantic spatial cells for each year from 1950 to 1999. The results indicate that the biomass of high trophic-level fishes has declined by two-thirds during the fifty-year period. Catches increased from 2.4 to 4.7 million tonnes annually in the late 1960s, and subsequently declined to below 2 million tonnes annually in the late 1990s. The fishing intensity for high trophic-level fishes tripled during the first half of the time period, and remained high during the last half of the time period. We estimate that the high trophic-level species contributed 53% to the value of total fish landings in 1950, and that this declined to 29% by the end of the century. Comparing the fishing intensity to similar measures from 35 assessments of high trophic-level fish populations from the North Atlantic, we conclude that the trends in the two data series are similar. Our results raise serious concern for the future of the North Atlantic as a diverse, healthy ecosystem; we may soon be left with only low trophic-level species in the sea

keywords     biomass saup landing

abstract
Fishing gears, instrumental to the fishing process, exert direct but often poorly documented impacts on marine communities and habitats. Analysis of global fishing patterns is now possible using a database that associates all global catch with fishing gear types. Maps prepared from this database are particularly useful to help assess the impact of fishing gears such as bottom trawls and dredges, which have been shown to have significant impacts on marine communities.

keywords     fishing gear, database, catch, trawl, dredge

abstract
Fishing gears, instrumental to the fishing process, exert direct but often poorly documented impacts on marine communities and habitats. A database is described here that associates all global catch with fishing gear types allowing for the analysis of global fishing patterns. The fine spatial detail of the Sea Around Us project?s catch database allows for the construction of maps showing subtle changes in the use of fishing gears annually since 1950. These maps are particularly useful to help assess the impact of fishing gears such as bottom trawls and dredges, which have been shown to have significant impacts on marine communities. Maps included in this report chronicle the expansion of these and other gears in ways that will inform debate over their impacts, and proved critical information to inform policy development and management choices

keywords     global,fishing gear,trawl

abstract
Alternative fishery management policies under different policy objectives for the 1990s Hong Kong waters ecosystem were explored using a newly developed simulation model named ?policy simulator? under the Ecopath with Ecosim software. Scenarios, which aim to maximize the economic output, the social output, the ecological output, and a compromise between the above three outputs were simulated under different vulnerability settings. Results suggested that policy simulations that aimed to maximize economic and social strategy were sensitive to vulnerability setting. Results from simulations aimed to maximize ecological stability and the compromise scenario are generally consistent between different vulnerabilities, and suggested that fishing effort of all fishing sectors and all except P4/8 fishing sectors, respectively, should be reduced. The study also demonstrated that the economic and social outputs decrease when policy objective focuses increasingly on maximizing ecological stability. The results are consistent with general observations of fisheries management. It is suggested that the ?policy simulator? offers excellent insights into management trade-offs in an ecosystem context.

keywords     model ecosystem policy Hong Kong China

abstract
The prawn trawl fishery in Exmouth Gulf, Western Australia, is well managed and harvests a mixture of penaeid prawns. Catches of the high value, brown tiger prawn Penaeus esculentus have comprised about 36% of the annual catch in the 1990s. However, annual catches of tiger prawns are now about half the level they were in the 1970s and fluctuate markedly, from about 200 to 680 t. These changes in catch create uncertainty in the supply of prawns for export markets and force fishing and processing operators to have excess capacity to deal with good years. Managers, fishing industry and researchers are considering the option of enhancing the natural recruitment of brown tiger prawns by releasing juveniles in wild nursery areas to reduce natural fluctuations and increase the average annual catch. This collaborative project (CSIRO, Fisheries WA, MG Kailis Group of Companies) assessed the feasibility of stock enhancement of tiger prawns in Exmouth Gulf by: developing a bioeconomic model, examining the risks of changes in the genetic composition and introducing disease to the wild population of tiger prawns, and identifying further work that would be needed before stock enhancement should proceed. This is the first stage in several stages that would lead to stock enhancement of tiger prawns in Exmouth Gulf. The project was initiated through a workshop of all project participants in Perth in July 1998.

keywords     shrimp Australia aquaculture model

abstract
Five separate commercial fisheries target the saucer scallop, Amusium balloti (Bernadi 1861) in Western Australian waters. While the average annual catch from these fisheries is around 600 tonnes of scallop meat, past catches have been highly variable with annual landings ranging from 150 to 4,400 tonnes of meat worth between $2 and $59 million. Consequently, scallops represent one of the larger single-species fisheries operating in Western Australia (WA). A. balloti has a distribution spanning most of the WA coast, from Broome in the north around to Esperance in the south. Despite this extensive distribution, saucer scallops tend to be restricted to areas of bare sand in the more sheltered environments found in the lee of islands and reef systems, and are consequently found in commercially viable amounts in only five locations in WA. The five WA fisheries that target scallops (with average annual landings in brackets) are: the Shark Bay Scallop Managed Fishery (541 t), the Abrolhos Islands and Mid-West Trawl Managed Fishery (121 t), the south coast (15 t), the South-West Trawl Managed Fishery (11 t), and the Nickol Bay Prawn Managed Fishery (4 t). The majority of the annual catch is exported as frozen scallop meat to Asia, Europe and the United States of America; while a small portion is marketed directly to the public via local retail outlets. As with catches, wholesale market prices have fluctuated dramatically over the last 10 years, plummeting from $16/kg in 1987 to $8.50/kg by 1991, before steadily improving to peak at $28.50/kg in 1995. This variation has arisen primarily in response to product availability and condition. The primary scallop fisheries operate in Shark Bay and around the Abrolhos Islands. Commercial fishing commenced in these fisheries in the late 1960s with moderate catches reported. Following a period of low catches in the mid 1970s, landings increased significantly during the late 1970s and early 1980s, mainly due to increased recruitment and fishing effort. Further advancements in processing methods and marketing strategies, and an associated increase in profitability, attracted even more vessels to the fisheries with further increases in effort. Subsequently, both were declared limited entry fisheries (now termed Managed Fisheries under the Fish Resources Management Act 1994). The Abrolhos Islands and Mid-West Trawl Fishery and Shark Bay Scallop Fishery were declared limited entry fisheries in 1986 and 1987 respectively. As A. balloti is an active swimmer, otter trawling is favoured. Vessels fishing for scallops in WA employ demersal otter trawl gear with strict controls placed on the vessels (boat units) and associated trawl gear (size restrictions) that can be used in each of the fisheries. These controls are designed to limit the total fishing effort to acceptable levels in order to maintain adequate spawning stocks, and to target those scallops at a size and age when the meat is in a premium condition for market. Research into the biological and environmental aspects of WA scallop stocks and their commercial exploitation has been carried out by Fisheries WA since the late 1960s. This research has centred on maximising the economic returns from the available scallop resource, while managing its use and harvesting at ecologically sustainable levels. Research initiatives have included pre-season surveys to monitor the strength of recruitment to seasonal scallop stocks; the monitoring of environmental influences, such as the Leeuwin Current, and their effects on scallop populations; and the provision of detailed catch data via voluntary logbook programs and statutory monthly fishermen?s returns.

keywords     scallop Australia fisheries

abstract
Simulation was used to improve the management of prawn fisheries by indicating patterns of fishing effort which favour the harvest of more highly valued, larger animals. Attempts to use conventional local optimisation methods to find the optimum pattern ofweekly fishing efforts were ineffective. Simulating annealing, a global optimisation method, was used effectively to find fishing effort patterns which maximised catch values. Sensitivity of the maximum catch value to the parameters used to model fishing and biological behaviour was also investigated. The optimum catch value was not sensitive to variations in trawl net selectivity or catchability parameters, although the optimum fishing season to obtain these maxima altered. In contrast, changes to biological parameters had a notable effect on the maximum catch value, despite compensatory changes to the optimum weekly pattern of fishing effort. The risk associated with achieving management goals using a range of fishing strategies was also assessed when recruitment timing and growth rates were modelled as partly stochastic. With uncertainty in recruitment timing, it was found that the optimum fishing pattern did not change. Uncertainty in growth rates made fishing earlier the best strategy , and increased harvest values in 43% of simulations.

keywords     shrimp model optimisation fishing

abstract
This work aims to determine the exploitation status of Hong Kong's inshore fishery resources, and the likely impact of management measures on the coastal ecosystem. This report describes results of the assessment work performed by the Fisheries Centre, UBC, between April 1996 and December 1997. Biomass and catch have been estimated by season and sector with survey data: from regular monthly samples of benthic resources using a prawn trawl, from samples of pelagic resources using a purse seine, and from catch estimated from an interview survey of fishers. Benthic biomass is also estimated in 18 spatial sampling strata. Prawns are included but the work does not cover shellfish. Total inshore resource biomass is estimated as about 9000 tonnes annual average ( = 4.9 tonnes km-2), of which 85% is comprised of pelagic species. There is a strong seasonal pattern, seen most strongly in the pelagic species, but also present in benthic resources, with total biomass peaking at over 27,000 tonnes ( = 15 tonnes km-2) in August and dipping to 1700 tonnes ( = 0.9 tonnes km-2) in February. These results are subject to uncertainties in estimating swept areas and in extrapolating from more detailed work on individual species. Based on estimating the probability distribution of the catch rates of individual vessels in seven gear sectors and by species, the total catch in Hong Kong waters is estimated as 14,700 tonnes (7.8 tonnes km-2). A detailed breakdown of this catch by gear sector and species is provided. Very wide confidence limits reflect a high variance in individual vessel catch rates, and the results are subject to considerable uncertainty deriving from the adoption of an interview protocol to estimate catch. Detailed assessments of exploitation status have been carried out for 17 individual species, four of which are crustaceans. Growth parameters and mortality parameters have been fitted to survey data, and age data derived from otolith readings. Growth is fitted by least squares techniques, length frequency analysis, and estimates take account of many published values from the literature. Mortality includes total mortality, estimated largely by cohort slicing, offshore migration with age for certain demersal species, estimated by a novel method, and present fishing mortality calculated by two alternative methods. Yield- and biomass-perrecruit analyses have been employed to evaluate exploitation status. Uncertainties have been explicitly defined and addressed through confidence limits placed on most estimates using Monte Carlo simulation techniques. Twelve of the 17 species are heavily overexploited, while the remainder, principally the small high-turnover species, fall into the fully exploited category. Very approximate sustainable yield estimations based on calculating unexploited biomass suggest that catches of larger and slower-growing species might be roughly doubled with optimal management. A major uncertainty is the equilibrium assumption made by all of these methods, that recruitment will not be greatly affected by increases in abundance. Multi-species bioeconomic analysis for the trawl fishery, based on parameters from the individual species, conflates the assessment optima for the individual species in terms of their relative value. The results suggest that long term yield for the 17 species might be roughly doubled by increasing mesh size, but are sensitive to assumptions made in estimating relative recruitment factors among the species. A trophic mass-balance model of the Hong Kong inshore ecosystem is constructed from information derived from the analysis and from the literature. The model includes shellfish, marine mammals, and all living components of the system. The model is used to predict the impact of six scenarios of changes in management on the relative abundance of sectors of the resource. Halving the current fishing mortality results in considerable benefits for all fishery sectors, and those with a conservation focus such as marine mammals. The full benefits of such a policy may, however, take a decade to be realised.

keywords     Hong Kong fisheries

abstract
While the first version of Ecosim (Walters et al. 1997) offered many facilities to mana-gers, it did not provide a means of describing the spatial relations of biomass and fishing mortalities which are required to examine the potential impacts of marine protected areas (MPAs). To overcome this, we devised a simple modification to Ecosim which allows the biomass of Ecopath groups to be partitioned into two portions with exchange processes operating between them.

keywords     mpa ecosystem ecopath model

abstract
Information from the unusual collapse and rebuilding of individual penaeid stocks within the Western Australian multi-species trawl fisheries assists in developing population models for penaeids and identities potentially vulnerable prawn stocks. The Exmouth Gulf stock of Penaeus merguiensisi collapsed in the 1960s and has not recovered. The P. esculentus stocks in Shark Bay and Exmouth Gulf suffered recruitment overfishing during the early 1980s, but significant reductions in the fishing effort directed at this species have resulted in increased breeding stock and improved catches; spawning stock-recruitment relationships have been developed for the two P. esculentus stocks. No such relationship is clear for the Penaeus latisulcatus stock in Shark Bay, but the data suggest that recruitment may be influenced by an environmental effect at the time of recruitment. The ability of a fishery to exert high levels of pre-spawning fishing mortality is a common factor in penaeid fisheries showing recruitment overfishing. Local geography, the position of the fishery within a species range, the presence of other species in a fishery, and the catchability, appear to affect susceptibility to overfishing.

keywords     shrimp fisheries

abstract
Simulation is used to improve the management of prawn fisheries by indicating patterns of fishing effort which prevent the harvest of under-sized animals, conserve sufficient breeding stock, and maximise the sustainable yield. Attempts to use conventional optimisation methods to find the optimum pattern of weekly fishing efforts have been ineffective because of the many extraneous local maxima. Through the use of global optimisation methods such as simulating annealing we have been able to find fishing effort patterns which maximise predicted catch values. Despite being continuous variables, the optimum levels of weekly fishing efforts usually assumed either values of zero or else the maximum fishing effort allowed. Sensitivity of the predicted maximum catch value and the pattern of fishing effort achieving this were examined for a range of parameter values representing the fishing (net selectivity and catchability) and biological (natural mortality and growth rate) processes. The greatest catch values obtainable were constant for a wide range of values of trawl net selectivities and catchability parameters, however, the optimum fishing season to obtain these maxima altered. In contrast, changes in biological parameters had a large effect on the maximum catch value despite compensation in the optimum pattern of weekly fishing efforts.

keywords     shrimp model optimisation

abstract
Simulation modelling was used to examine the benefits of seasonal and spatial closures of two prawn fisheries which differed in their recruitment patterns; one had a single recruitment pulse (annual) while the other had two each year (biannual). An optimization procedure was used to assign monthly fishing effort (within realistic constraints) which would maximize annual catch value. Reductions in values resulting from uncertainty in recruitment timing were examined. An 'ideal' pattern of monthly fishing effort for each fishery was fitted using an exhaustive search method because other methods could not find the global optimimum. Catch values resulting were used as a basis of comparison within each fishery with closure results. For the annual fishery, the best seasonal closure produced 98% of the value of the 'ideal', spatial closures 102%, and combined seasonal and spatial closures 104%. Relative values for the biannual fishery were similar except for combined closures which produced 116%. Generally, however, spatial closures outperformed combined and seasonal closures when recruitment timing was uncertain. Egg production was generally 30-40% of an unfished stock and was highest for combined closures.

keywords     simulation model shrimp fisheries mpa

abstract
Knowledge of recruitment patterns is a requisite for modern fisheries management. These patterns can range in complexity from a single pulse of identically sized and aged prawns, which is often assumed in fisheries models, to continuous recruitment by prawns of several ages. Existing techniques used to identify recruitment patterns range from the ad hoc use of size limits to more complex methods that examine changes in length-frequency modes through time. A model that allowed variable growth of individuals was used to simulate monthly length-frequency fisheries data from a range of recruitment patterns of varying complexity. The effectiveness of a range of methods to identify these underlying recruitment patterns was examined. Length-frequency survey data from tropical penaeid fisheries for Penaeus esculentus, the brown tiger prawn, in two locations off north-eastern Australia (Torres Strait and Turtle Island Group) were also subjected to these methods. Methods that employed simple truncation by length successfully identified simple recruitment patterns but were not effective for multi-age recruitment patterns. Only the length-cohort and age-cohort methods could identify the presence of older recruits in multi-age patterns. All methods were sensitive to estimates of growth parameters, particularly the cohort-based methods. Results suggest that P. esculentus from the two fisheries examined had different recruitment patterns requiring different management approaches.

keywords     shrimp recruitment model

abstract
We used simulation modelling to find seasonal closures which maximized either yield per recruit (Y/R) or relative value per recruit (V/R) for several tropical shrimp fisheries. Each case examined represented a choice of (1) a single versus a multicohort population, (2) the reduction of annual fishing effort levels through closures versus its redistribution to the fishing season, and (3) a range of fishing mortality levels. Under most conditions, seasonal closures which maximized Y/R also maximized V/R, though simulated gains in the latter were smaller. Timing of seasonal closures was more critical for fisheries of single-cohort populations than multicohort populations. Multicohort-based fisheries required shorter seasonal closures to maximize V/R than did those based on single-cohort populations. Assumptions about the disposition of fishing effort normally expended during the period of a seasonal closure greatly affected the best closure choice. Predicted best closures were of a longer duration when annual fishing effort was simply redistributed rather than reduced by closures. Greatest improvements in Y/R (30 to 40% ) were obtained for fisheries based on singlecohort populations when closure effort was redistributed. Predicted increases in Y/R for multicohort-based fisheries never exceeded 7%. The duration of best closures increased with increasing values of fishing mortality when the annual fishing effort was reduced by closures. This trend was reversed when annual fishing effort was conserved. As fishing mortality increased, potential gains in Y/R or V/R improved at the cost of equilibrium egg production.

keywords     shrimp model optimisation

abstract
From aerial photography (July 1987) and diving surveys (February 1988), 876 ha of seagrasses (eight species) were mapped in Cairns Harbour, tropical north-eastern Queensland. Zosteru cupricorni was the most common seagrass species and had the greatest biomass at 79 9 m-2 dry weight of stems and leaves and 180 9 m-2 dry weight of roots and rhizomes. The maximum shoot density found was 4798 shoots m-2 of Hulodule pinijoliu, the second most common species. Seagrasses were found only between 0.5 and 5.0 m below mean sea level. Zosteru cupricorni was found at the shallowest depths, Hulodule pinifoliu at the deepest depths. Twenty species of penaeid prawns, nine of which are marketed commercially, were sampled from the seagrass beds. Abundances of prawns of commercial species were significantly greater on seagrass-covered substrata than on nonvegetated substrata. Overall, 5614 mostly small or juvenile fish, representing 134 taxa, were sampled from seagrasses in Cairns Harbour. The most numerous fish species were a goby, Yongeichthys criniger, and a pony fish, Leiognuthus splendens. Only 15 species were highly valued as recreational fish, and only 11 species were highly valued as commercial fish. Of the fish species, five (4%) were highly valued species of both groups. The density of fish on the seagrass beds was estimated to be 8809 fish ha-1.

keywords     seargrass shrimp habitat Australia

abstract
Concern over the loss of seagrass habitat has prompted examination of the value of the production of commercial prawns from such habitat. Cairns Harbour in tropical northern Queensland has 876 ha of mixed seagrasses, dominated by Zostera capricorni and Halodule pinijolia, that support a multispecies commercial penaeid prawn fishery offshore. Densities of juvenile commercial prawns estimated from seagrass surveys were used to project estimates of annual yield and landed value, using a deterministic simulation model employing lunar-period time steps. Estimates of the potential total annual yield from Cairns Harbour seagrasses for the three major commercial prawn species (Penaeus esculentus, P. semisulcatus and Metapenaeus endeavouri) were 178 t (range 81-316 t) year-1 with a landed value of .2 million (range $0.6 million to $2.2 million) year-l.

keywords     shrimp value yield seagrass Australia model simulation

abstract
Seasonal fishery closures are commonly used in fisheries management for various purposes, including limitation of effort, protection of spawners, and maximization of the yield or value that can be obtained from a cohort. The effectiveness of a proposed closure can be evaluated through yield-per-recruit analysis, which can be carried out analytically for some simple situations. For other fisheries, such as the penaeid shrimp fishery of Torres Strait, Australia, investigated here, the analyses are more complex because recruitment occurs in pulses throughout the year and the intensity of fishing is itself unevenly distributed in time, being patterned after these recruitment pulses. Furthermore, the imposition of closures of different durations has been documented to alter the pattern and intensity of fishing after the fishery reopens. In this study, a simulation approach is used to identify the timing and duration of closures that are likely to increase the yield or the value per recruit of the fishery. The simulation allows for changes in the distribution and magnitude of effort directly caused by the closures. All input parameters are assumed to be known precisely, except those controlling fishing and natural mortality, which are drawn from empirically derived ranges. The simulation results indicate that a 6-month closure starting in December or January could increase the value of the fishery by 5-10%, compared with a fishery with the same fishing pattern and no closure.

keywords     model shrimp simulation optimisation fleet model

abstract
Spatial closures are commonly used by Australian fisheries managers to alter fishing patterns. To evaluate different fishing closures, however, fishery scientists have to understand and model the spatiotemporal interactions between fish stocks and fishing fleets. We develop a deterministic, stationary, per-recuit, age-structured simulation model to assess different spatial closure strategies, and use date from the Torres Strait tiger prawn fishery, Penaeus esculentus, as a working example. Our results show that selection of an optimum spatial closure largely depends on the relative importance given to changes of the different utility functions evaluated (yield, value, egg production). We show that, on average, with a spatial closure yield-per-recruit would decrease, but also show that value-per-recruit may increase 10% with the appropriate closure. Our results suggest that egg-per-recruit would always increase in the presence of a closure. By incorporating parameter uncertainty within the simulation model we predict the uncertainty associated with alternative closure strategies, and thus provide valuable information for the decision-making process.

keywords     simulation shrimp Australia closure model

abstract
Spatial closures are imposed by resource managers to prevent the operation of fishing fleets in certain areas of a stock's distribution. In Queensland, east coast trawl closures are usually located in shallow waters to prevent fishing of prawns before they reach an optimum marketable size and migrate offshore. The success of such fishery controls should be measured by careful analysis of the benefits to fishery production, and the costs and practicality of enforcing the regulation. The potential of simulation models to investigate optimising fishery production by adjusting the starting date, length and extent of a fishing closure has been established in the Torres Straits tiger prawn fishery. It was predicted that by modifying the length and starting dates of seasonal closures that gains of up to 15% in yield-per-recruit and value-per-recruit could be achieved. By comparison, the best gains predicted by adjusting the boundaries of permanent spatial closures were less than 10% of value-per-recruit and negligible for yield-per-recruit. Enforcing fisheries regulations is expensive and especially difficult in the case of spatial closures. Most fishers are aware of this difficulty and some fish in closed areas because of the competitive advantage and the short-term benefits this practice provides. Therefore, it is important to evaluate the level of non-compliance which would dissipate the benefits gained from any closure regulations. In this paper the effect of cheating is evaluated by value-per-recruit and egg-per recruit analysis.

keywords     value compliance closure model simulation Australia

abstract
Daytime catches ofjuvenile penaeid shrimp from two modified sledges (providing stimulation by water-jet or electric current) were compared with catches from a conventional sledge ( or beam trawl ) used at night. The results indicate that the daytime use of a water-jet sledge is a suitable alternative when night-time sampling is precluded. Mean catch rate of the Brown tiger prawn (Penaeus esculentus) in the daytime water-jet sledges was not significantly different from the night-time conventional sledges. but catches in the daytime electric trawls were significantly less. In contrast, the catches of the Endeavour shrimp (Metapenaeus endeavouri) and the Greentail shrimp (Metapenaeus bennettae), in both the daytime water-jet and daytime electric sledges, were significantly lower (approximately one-quarter) than in the night-time trawls. There was no significant difference between the length frequency distributions of P. esculentus, M. endeavouri or M. bennettae caught in the conventional night-time and in the daytime water-jet sledges.

keywords     shrimp sampling

abstract
We present an approach to the analysis of crustacean egg production ogives with emphasis on detecting seasonal trends. The relationship between the proportion of gravid females (by size) and season is a prerequisite to the estimation of egg production potentials of populations. The basic method consists of relating, for each sample, the proportion of berried females with their size through a three-parameter logistic function where the asymptote may be less than 1. We then provide guidance for detecting seasonal trends in the estimates of the parameters for the individual samples. This is accomplished by restricting the basic model such that some parameters are considered to be either fixed for all samples or as simple functions of time or environmental variables such as temperature. Parameter estimates are obtained via maximum likelihood methods, and comparisons between alternative models are presented graphically and using likelihood ratio tests. We illustrate the approach and its application with data for a tropical shrimp, Penaeus esculentus, from northern Australia. Nous presentons une approche pour I`analyse des enveloppes d`oeufs de crustaces qui insiste sur la detection des tendances saisonnieres. Le rapport entre la proportion de femelles gravides (par taille) et la saison est un prerequis pour I'evaluation du potentiel de production d'oeufs des populations. La methode de base est basee sur I'etablissement de rapports, pour chaque echantillon, entre la proportion des femelles porteuses d'oeufs avec leur taille grace a une fonction logistique a trois parametres dont I'asymptote peut etre inferieure a un. Nous don nons ensuite des conseils permettant de deceler les tendances saisonnieres dans les evaluations des parametres d'echantillons individuels. On y arrive en restreignant le modele de base de facon a ce que certains parametres soient consideres comme etant soit fixes pour tous les echantillons, ou soit de simples fonctions du temps de variables environnementales comme la temperature. Des evaluations de parametres sont obtenues par la methode de la vraisemblance maximum et des comparaisons entre plusieurs modeles possibles sont presentees graphiquement et utilisent des tests de rapports de ressemblance. Nous illustrons cette approche et son application avec des donnees obtenues pour une crevette tropicale, Penaeus esculentus, provenant du nord de l`Australie.

keywords     shrimp reproduction model crustacean

abstract
An accurate estimate of abundance is essential for fisheries management. Abundance estimates are often limited, due to insufficient information regarding the catch efficiency of the sampling gear. A measure of sampling gear efficiency will enable a realistic estimation of abundance. Trawl sampling gear efficiency, is the proportion of animals retained in the net relative to the total number in the path of the trawl (Kjelsohn and Johnson 1978). Estimating the efficiency of the sampling gear often causes serious problems for the analysis of trawl survey data. Gear efficiency involves many complex variables that are often insufficiently understood to predict their cumulative effects. The efficiency of trawl sampling gear varies not only for each species but also for different size classes and with varying environmental conditions (Kjelsohn and Johnson 1978). This unmeasured variability in trawl sampling gear efficiency, results in an error in estimating population size. Measuring this error remains a major and largely unresolved challenge in fishery science. Selectivity is closely related to gear efficiency and includes components of net mesh selectivity and fish or prawn behaviour. Mesh selectivity is the variation in fishing mortality with age, which is the differential escape of certain sizes of fish or prawns after they enter the mouth of the net (Gulland 1983). Both efficiency and selectivity describe in some way the performance of gear. The distinction made is that efficiency is a measure of the gear's catch relative to the total population present in the area swept by the net. Mesh selectivity is a measure of the gear's catch relative to the number of prawns that entered the mouth of the net. Gear efficiency includes the effects of mesh selectivity and any other processes of selectivity that occur when fish or prawns are initially stimulated from the sea bed into the mouth of the trawl. " Errors that occur in these calculations affect the estimates of absolute abundance and the shape of length-frequency distributions. Errors in length-frequency distributions are due to the size-specific nature of sampling trawl gear efficiency. Errors in estimates of absolute abundance are due both to the size-specific nature of the trawl, and to species-specific factors such as diurnal and seasonal variations in behaviour. Other factors that affect trawl efficiency are associated with the physical aspects of the fishing gear itself (Table 1 ). These factors have an importance that is often not fully appreciated in fisheries research. It is imperative that these factors are closely monitored during survey work to ensure that inter-sample variation of trawl efficiency is minimized. Commercial trawl gear designs compromise gear efficiency to achieve a practical and safe operation. The designs are selective for commercial species and sizes. They may be strongly biased against catching trash species and collecting debris even to the extent of having a negative effect on their commercial catch.If using commercial gear in fisheries research it may be necessary to be aware and correct for any bias that may exist. We conducted two separate experiments for efficiency and selectivity in order to investigate sample bias. Experiment 1 was designed to measure the size-specific trawl efficiency. Experiment 2 investigated mesh selectivity in greater detail. Experiment 1 is reported in full. The results presented for Experiment 2 incorporate data from only the first two monthly surveys and provides a preliminary examination of the selectivity performance of a standard port net relative to a small mesh starboard net.

keywords     trawl Australia

abstract
Regular monthly sampling at eight trawl sites in Great Barrier Reef waters identified variations in both species composition and the relative abundance of the more common species over a 2-year period. Faunal composition was affected more by the location of sample sites than by the time when samples were taken. Ordination analysis differentiated a 'nearshore' group of sites from a 'midshelf' and an 'inter-reef' group. The composition of 'inter-reef' fauna remained strikingly uniform below the 40 m depth contour regardless of proximity to coral reef formations. Classification of the samples also revealed weakly separated 'wet' and 'dry' season temporal groupings, with the former characterized by higher abundances of several 'nearshore' species.

keywords     bycatch trawl shrimp Australia

abstract
Torres Strait is a tropical body of water lying between the tip of the Cape York peninsula and the south coast of Papua New Guinea and bordered on the east and west by the Coral Sea and Arafura Sea respectively (Figure 1 ). The strait is shallow, usually less than 15 m deep. It extends 100 km north-south and 20 to 60 km east-west (Wolanski 1986). This region has extensive coral reefs, numerous coral cays and some continental islands. There are more than 70 islands throughout the Straits' 8 000 km2 sea area. Seventeen of these are inhabited by Islander communities (Bain 1986). The largest reefs in Torres Strait are the Warrior Reefs which extend for 65 km roughly north-south, bisecting the region and separating the Coral Sea to the east from the Arafura Sea to the west. Torres Strait is separated from the deeper waters of the Coral Sea by a ribbon of reefs which are a continuation of the outer Great Barrier Reef. Immediately to the east of the Warrior Reefs is the Great North East Channel. This channel is 20-40 m deep and continues as far as Papua New Guinea making it important as an international shipping route. It is this region where most of the Torres Strait fisheries are located (Anon. 1987a).

keywords     DP/CU:REPT20:322 Australia fisheries

abstract
Management needs for zonation of the central Great Barrier Reef Marine Park by user activity prompted a study of the demersal trawl fauna from a range of sites. Cluster analysis revealed three distinct site assemblages: 'coastal' , 'inshore' , and 'inter-reef' , characterized by the conspicuous abundance of some species and the absence of other species. The location of these assemblages was related to water depth, sediment particle size composition and distance offshore but could not be explained by the distribution of fishing effort. Some sites, intermediate in location between these assemblages, were assigned to a 'transitional' assemblage in which sites changed affiliation temporally.

keywords     bycatch reef shrimp Australia

abstract
The velvet shrimps, Metapenaeopsis rosea (Racek and Dall 1965) and M. palmensis (HasweIl1879), form a large part of penaeid shrimp catches from Torres Strait, Queensland, Australia, and are caught from 5 to 30 mm carapace length. Recruitment to the fishery occurs annually in January to March and abundance is greatest during May to October. Females are first found mature at 12 mm carapace length and spawning occurs year-round with peaks in April, July and October. Males begin to mature at 5 mm carapace length and all have joined petasmas by 9 mm carapace length. M. rosea males are heavier than their female counterparts at any given carapace length and no difference was found between male and female M. palmensis. Male and female M. rosea were heavier than those of M. palmensis at the same length. Until recently catches of these species were discarded but increasingly those of larger sizes are retained and marketed.

keywords     shrimp biology Australia

abstract
Penaeus esculentus, the brown tiger prawn, is endemic to Australian waters (Grey et al. 1983). It is found northward from southern New South Wales, through the Gulf of Carpentaria and around to Shark Bay ir Western Australia (Grey et al. 1983). Torres Strait is the most northerly extent of its distribution. Catchl P. esculentus form the main component of catches from the Torres Strait Prawn Fishery (Section 2). Except for the habitat utilized by the juvenile stage, in Torres Strait P. esculentus conforms to the penaeid life cycle as outlined by Garcia and Le Reste (1981 ). Juvenile P. esculentus in this region, use seagrass beds on reef-platforms as nursery areas (Section 4), and not estuaries as in other brown tiger prawn fisheries. Information on spawning and recruitment patterns of P. esculentus is essential to the implementat of management strategies such as temporal and spatial closures and effort limitation. However, there is life history information available for this species in Torres Strait. Studies on the reproductive activity of I escu!entus in the Gulf of Carpentaria (Crocos 1987; Buckworth 1985; Robertson et al. 1985) found main spawning periods from July-November. Other studies on P. esculentus in Torres Strait (Somers et al. 19: and the Low Islet region of the East Coast Prawn Fishery (O'Connor 1979) found a major spawning peril occurred in March. Information on P. esculentus recruitment patterns is confusing. Recruitment to the fishery of subadults ( < 26 mm carapace length) occurred from March-May in the Exmouth Gulf (Penn and Caputi 191 and November-March in the Gulf of Carpentaria (Somers et al. 1987b). In Torres Strait, Somers et al. (1987a) found continuous recruitment to the fishery of P. esculentus from March-September followed by decrease in December. The differences in spawning and recruitment periods between the Torres Strait, Queensland East Coast and the Northern Prawn Fisheries, poses a problem for fisheries managers with regard to blanket management policies for P. esculentus. This study provides biological information on spawning and recruiment timing of P. esculentus in Torres Strait. This information can be used to formulate management strategies designed to maintain high yields in the short term, and long term productivity of the Torres Strait Prawn Fishery. 5.2 Materials and Methods 5.2.1 Selection of samolinfJ ~t~ti()n,

keywords     DP/CU:REPT20:326 Australia shrimp recruitment spawning biology

abstract
Some of the most important factors in managing a fishery are: an estimate of the relative abundance of the population, the age/size composition of the population, growth rates, age at maturity, and mortality rates from fishing and natural causes (Rounsefell 1975). As juvenile prawns are found in a separate habitat from that of adults, prawn movements are also important to management. Tagging of animals for later recovery is an excellent method for estimating growth rates and migration, and for separating fishing and natural mortality rates (Gulland 1983). In some instances tagging can also be used to estimate population size (Jones 1977). Several assumptions are made concerning tagged individuals. Firstly, that the tagged individuals disperse randomly through the population to be studied before recapture, secondly that the tagged individuals are subject to the same mortality rates as untagged individuals, and thirdly that tags are not lost or overlooked when recovered (Krebs 1978). In some circumstances it is impossible not to violate one of these assumptions. Tags are known to affect speed of movement, susceptibility to predation, feeding ability and mortality (Rounsefell 1975). Despite these violations, tagging is the most reliable method for estimating growth in Penaeidae (Garcia and Le Reste 1981 ). Another reliable application of tagging experiments is to quantify the movement of tagged animals. A knowledge of migration patterns is an essential component in the identification of stock boundaries (Somers and Kirkwood 1984), an issue of importance for the Torres Strait Prawn Fishery which has catch sharing arrangements between two countries, Australia and Papua New Guinea. The initial objectives of this tagging programme were to describe the movements and growth of Penaeus esculentus, the brown tiger prawn.

keywords     DP/CU:REPT20:328 Australia growth movement shrimp tagging

abstract
In the past, management of the Torres Strait Prawn Fishery has relied on the reproductive biology and larval and juvenile abundance information on Penaeus esculentus, brown tiger prawn, from the Northern Prawn Fishery and the Queensland East Coast Prawn Fishery. Seasonal trawling closures in Torres Strait are adjusted to coincide with the main seasonal closure in these areas (Section 1 ). Metapenaeus endeavouri, endeavour prawn is often taken in association with P. esculentus (Grey et al. 1983). Although M. endeavouri is a major contributor to the commercial prawn landings of Torres Strait, very little information on its reproductive biology is available compared with P. esculentus. As the commercial catch of the Torres Strait Prawn Fishery increases (Section 2), knowledge of the reproductive biology of the penaeid prawns present in Torres Strait is required for management purposes. The reproductive biology of P. esculentus has been investigated in the Gulf of Carpentaria (Northern Prawn Fishery) (Buckworth 1985; Robertson et al. 1985; Crocos 1987b), Exmouth Gulf (Western Australia) (Penn and Caputi 1986) and the Low Isles (Queensland East Coast Fishery) (O'Connor 1979). Somers et al. (1987), investigated the reproductive activity of P. esculentus and M. endeavouri in Torres Strait. Interpretation of this study was restricted due to the three-monthly interval between sampling periods (Courtney and Dredge 1988). To enable documentation of the reproductive patterns and spawning seasons for the commercial prawn species in Torres Strait, an egg production index or a PFI (Population Fecundity Index) has been estimated. Population fecundity is the sum of the fecundities of all the females in a population (Bagenal 1973) and can be expressed in terms of an index of population fecundity (PFI) which is the number of eggs produced or potentially produced by a population. This measure has been used in combination with estimates of spawning frequency to document spawning seasons (Penn 1980). Past calculationsof a PFI for penaeid species (Penn 1980; Crocos and Kerr 1983; Crocos 1987a and 1987b; Courtney and Dredge 1988) have incorporated the proportion of female spawners in the population, their length distribution and the relationship between an individual female's fecundity with its carapace length. The PFI calculated in this study does not incorporate the proportion of female spawners in the population but uses the number of female prawns with mature ovaries per square metre of seabed swept by trawl nets as estimated from our surveys. This method is equivalent to the methods used in other reproduction studies on P. esculentus (O'Connor 1979; Buckworth 1985; Robertson et al. 1985), except these studies identified spawning peaks from the proportion of females with mature ovaries in a population (Crocos 1987a). To assess the true reproductive potential of a female prawn, the probability that it will be inseminated and therefore have fertile eggs must be determined. Crocos and Kerr (1983), Crocos (1987a and 1987b) and Courtney and Dredge (1988) studied the proportion of inseminated female penaeids but did not, however, incorporate this information into their egg production index or PFI. In this study, probability of insemination of ripe females has been incorporated into the PFI calculations. The aim of this report is to investigate the reproduction dynamics of both species to facilitate study of spawning seasonality and spawning areas for future management of the Torres Strait Fishery.

keywords     DP/CU:REPT20:327 shrimp Australia biology

abstract
This report presents some of the results from three years of research in Torres Strait. Some of the sections cover research which is presently ongoing and therefore are truly provisional in nature, while other sections have been reported in full as those phases of our research are completed. All sections presented in this interim report are esselltial to meeting our project's objectives {Section 1 ), as we could not restrict our research to surveys of adult commercial catches and historical studies of the fishery. It was necessary to study aspects of adult reproduction and juvenile development and to initiate tagging studies to understand and elucidate the life-cycle of the commercial prawn species Tagged prawns also allowed migration and growth rates to be monitored. It was necessary to investigate the use and performance of various survey gear to quantify estimates of juvenile and adult prawn numbers. Though this work was not an end in itself, it increased our understanding of prawn behaviour and revealed the potential sources of error in our survey estimates. Velvet prawns are not fished commercially in Torres Strait as they are in other north Queensland fisheries. We included them in our study for a two-year period because they were numerous, they are important to many other fisheries in the Indo-Pacific region, and they are of potential commercial value in Torres Strait. This work is now complete and it greatly increased our understanding of these species. Our surveys for juvenile prawns in seagrass areas often captured large numbers of other species, most notibly smaller fish species. Some of these are known to be major predators of juvenile commercial prawns. By retaining these fish specimens from beam trawl samples we were able to greatly expand our knowledge of potential prawn predators and of the community structure of seagrass habitats. Gathering information on the basic biological parameters of the commercial prawn species is time consuming. Often there is no completely satisfactory way of assessing the precision of our estimates of important things such as growth rates. A few years study of such a complex system as the Torres Strait Prawn Fishery does not allow much insight into the variability of these parameters between areas, years, and sometimes species. Though there is a strong desire for us to continue to improve our estimates and our understanding of the processes involved, this refinement would ultimately occur at the expense of our commitment to fisheries managers who require information on the relative merits of management options in real time. Key biological or population parameters can be combined with historical data in new or existing models of the fishery. The creation of these models test our understanding of the system. Our models can be refined as our understanding develops and through this process we can redirect our existing research to gather further information on key parameters or processes, or initiate research on important components that have been overlooked. We can use our models to test the possible impacts of different management scenarios once our models adaquately represent our understanding of the system and produce predictions which can be verified. Though the model predictions can often not be tested directly, they nevertheless represent our best estimate of the possible outcome of a management measure given our understanding of the fishery. In this way we can provide fisheries managers with the best information possible on which to base management decisions.

keywords     DP/CU:REPT20:334 Australia shrimp

abstract
Commercial prawn trawling has occurred in Torres Strait since 1974 and now produces 1000 tonnes annually (Section 1 ). Three main species of penaeid prawns are taken commercially: Penaeus esculentus, the brown tiger prawn, Metapenaeus endeavouri, the endeavour prawn and P. longistylus, the red spot king prawn. P. esculentus and M. endeavouri together make up 90% of prawn landings for Torres Strait. P. esculentus dominates prawn catches and are the most sought after because the highest export prices are paid for this species. Fishing effort in the Torres Strait Prawn Fishery is concentrated in the early months of the year. This coincides with a peak in recruitment of small P. esculentus (Section 5). Prior to implementation of seasonal closures to fishing, fishing effort was more evenly applied throughout the year. The Torres Strait Prawn Fishery is subject to an international treaty which calls for joint catch-sharing and management arrangements between Australia and Papua New Guinea. Total allowable catch quotas, closed fishing seasons, vessel and gear restrictions and closed areas are employed in its management. The geographical extent of the fishery, the location of those areas currently closed and the areas of national jurisdiction are shown in Figure 1. Fisheries management requires detailed catch and effort data over a long time so that trends can be observed and possible population changes can be predicted, and the disaster of a failed fishery hopefully avoided. The Northern Prawn Fishery (NPF) logbook data is the only source of information which permits analysis of spat~al and temporal trends of catch and effort in the Torres Strait Prawn Fishery (Section 2). Logbook records provide total effort (hours trawled) and catch (kg) data for P. esculentus, M. endeavouri, P. longistylus, and other unidentified species of prawns at a spatial resolution of about 11 km2. Records are available from 1980 to the present. This study examines the spatial and temporal fishing patterns of the Torres Strait prawn fleet from 1980-86 based on NPF logbook records and relates these fishing patterns to P. esculentus recruitment patterns (Section 5).

keywords     DP/CU:REPT20:324 shrimp Australia effort fisheries

abstract
Records of prawn catches in Torres Strait were poorly recorded during the developmental years of the prawning industry. Information collected by officers of the Northern Fisheries Unit in Cairns shows that in 1973-74 about ten prawn trawlers regularly fished Torres Strait, producing an annual catch of between 100 and 120 t. Catches consisted of mainly Penaeus esculentus, brown tiger prawns, and also Metapenaeus endeavouri, endeavour prawns. Prices at this time averaged $1.20 kg-1 for tiger prawns and $1.00 kg-1 for endeavour prawns. These vessels fished mainly from June to December in Torres Strait, after the end of the P. merguiensis, banana prawn, season in the Gulf of Carpentaria. Following ratification of the Torres Strait Treaty between Australia and Papua New Guinea in 1985 a management area, the Torres Strait Protected Zone (TSPZ), was defined under the jurisdiction of the Protected Zone Joint Authority (Section 1 - Figure 1 ). Although legally distinct from the two adjacent prawn fisheries, the Northern Prawn Fishery (NPF) and the Queensland East Coast Prawn Fishery, management of the Torres Strait Prawn Fishery has been run as part of the East Coast Prawn Fishery. With the introduction of joint management of Torres Strait fisheries with Papua New Guinea it became important to examine existing catch data for historical trends. The introduction of prawn catch quotas required by the Torres Strait Treaty relied on past catch records. This section collates historical catch data and examines trends in catch and effort.

keywords     DP/CU:REPT20:323 shrimp Australia landings

abstract
Velvet prawn is the FAO common name (Holthius 1980) given to a group of small penaeid species caught in tropical-temperate waters. Metapenaeopsis rosea Racek and Dall, 1965 (pink velvet prawn or rosy prawn) and M. palmensis (Haswell, 1879) (southern velvet prawn) are the two most abundant of five Metapenaeopsis species taken by trawlers operating in Torres Strait. M. rosea is an Indo-Pacific prawn of minor commercial importance. Distribution of M. rosea is restricted to northern Australia (particularly in the vicinity of the Great Barrier Reef) (Racek and Dall 1965), from Mackay (Queensland) through the Gulf of Carpentaria to Darwin (Northern Territory), and the northeastern Arafura Sea (near Irian Jaya) (Grey et al. 1983). The distribution of M. palmensis is more extensive and they are of commercial importance in some areas. They form over 15% of the prawn catch in small trawl operations in some areas of central Japan (Hayashi and Sakamoto 1978). This species is found in waters of eastern Borneo, Indonesia and Papua New Guinea (Racek and Dall 1965) and is the most dominant species of Metapenaeopsis in the Batan Bay and Tigbauan-Gimbal waters in the Philippines (Motoh et al. 1977). In the Gulf of Thailand, small M. palmensis are taken as bycatch and are sold as a dried product (Yoo-Sook-Swat and Thubthimsang 1988). Within Australia, M. palmensis is found in warm temperate and tropical northern Australian waters from Shark Bay (Western Australia), through to Sydney (New South Wales) in the east, but is much more common in waters along the northeastern coast (Racek and Dall 1965). Over twenty Metapenaeopsis species are distributed widely throughout the world. Approximately nine species are found in Australian waters (Racek and Dall 1965). Other species of Metapenaeopsis caught in trawls in Torres Strait are M. novaguineae (Haswell, 1879), M. lamellata (de Haan, 1850) and M. mogiensis (Rathbun, 1902). Metapenaeopsis species are found in waters of South East Africa (Racek and Dall 1965; Racek and Yaldwyn 1970; Champion 1973), North and South America (Huff and Cobb 1979; Bauer 1985), Malaysia and Indonesia (Racek and Dall 1965; Racek and Yaldwyn 1970; Hall 1962; Johnson 1976; Kubo 1949; Tseng and Cheng 1980), India (Suseelan et al. 1982; Dutt and Ramaseshaiah 1986), South China Sea (Kubo 1949; Hall 1962; Tham 1968b; Tseng and Cheng 1980; Johnson 1976), Melanesia (Hall 1962; Racek and Dall 1965; Racek and Yaldwyn 1970; Johnson 1976), Arabian-Persian Gulf and Red Sea (Miquel 1984). Despite their wide occurrence, few details are known of the biology of the Metapenaeopsis species in Australia, perhaps because M. rosea and M. palmensis are not specific targets of trawl fisheries in Australia. They are taken as by-products in fisheries for other penaeid species ( Grey et al. 1983). Catches of these species are not usually recorded by fishermen and are discarded. In recent years it has become common for larger sizes to be retained and marketed. Information on distribution, abundance, and maturation is necessary as their exploitation increases, if management of the fishery is to succeed. This study addresses these needs and represents the first detailed life history study of these species from Australia.

keywords     DP/CU:REPT20:329 shrimp Australia Metapenaeopsis

abstract
Managers of fisheries have always sought to predict the consequences of any management measure before it is introduced. Even broad predictions have proven extremely difficult to make and, mistakes in predictions can be costly to the industry and possibly the long term durability of the fishery. The industry expects management measures to be precise. For example the optimum dates for seasonal closures are expected to have an accuracy measured in weeks, if not days. Many of the management measures being employed on prawn fisheries in Northern Australia are novel in their application, for example, seasonal closures to protect small prawns have been in use for less than ten years in northern Australia. Few if any experimental controls have been used to establish the effectiveness of these measures. Large inter-year variations in prawn numbers occur naturally and can complicate long-term assessments. In response to industry concern, several different management regimes have been used in successive years, making the explanation of results extremely difficult because of their possible interactions. To assess the response and elasticity of a fisheries' potential to withstand fishing pressure it is usually necessary to employ widely varying levels of exploitation and then observe the response. This means some degree of calculated under fishing exploitation and over fishing exploitation within the fishery. To be successful these 'experiments' have to be large in scale and extend for several years. The very idea of costly manipulation of a viable important fishery is, at least for the present, politically unacceptable. This means that researchers are asked to help managers decide on strategies without the benefit of the type of data from the system which would allow statistical predictions to be made. They must therefore employ data from other fisheries. Fisheries from which data is available are often from temperate regions, and all too often are failed fisheries and not ideal for comparison with a tropical prawn fishery. There is one other tool researchers and managers can employ. This tool is simulation modelling. A fisheries biologist can estimate a number of important biological and population parameters from direct measurement, experimentation, or from the scientific literature. These can be combined with information gathered from economists, commercial processors and fishermen to produce a series of rules and relationships. Such controls often govern the fishery through various limiting factors such as the number of vessels, the available searching time, the biology of the key species, or the economics of the products. One or more of these aspects can be combined using the computational powers of computers in a simulation of the fishery. These computer simulations often allow for graphical or tabular display of the results so that all potential users can visualise the results and gain some understanding of the interplay between the many complex relationships underlying the model. Several types of computer simulation models exist. As the name implies they are meant to simulate the fishery. Given suitable input such as the numbers and sizes of animals recruiting into the fishery, models can produce estimates of potential outcomes. These may be landings, numbers of animals the following year, or even net profits. Most of these simulation programs are based on dynamic models. Dynamic models attempt to model the passage of time in the life of the fishery. Some programs model time on a continuous basis, while most models use discrete time units. Units of years are applicable only to comparitively long-Iived animals. For prawns, units of months or even weeks are more appropriate. The time scale most appropriate is dependent on the generation time of the key species as well as the detail available in the input data, and the precision required of the predictions. Many models use fixed rules to relate the input data to outcomes and do not allow for chance circumstances, these are deterministic models. Others attempt to simulate the natural uncertainty in the reaction of one factor in the fishery to others, or the certainty or potential error in the input data. These models allow for random or pseudo-random processes to occur. These stochastic models produce different results every time they are used even if the same input data is used. While this produces a more realistic approximation of the natural situation, it requires additional information on the rules which regulate how this variation or randomness occurs. When stochastic models are used, it is common to reuse the computer model a number of times, through the process of Monte Carlo simulations, in order to extract the average result. In addition to the average outcome, stochastic models also allow the range of expected results to be determined. Models can be either extremely complex or 'reductionist' in nature and attempt to desc~ibe all knowable aspects of the animals' biology and the fishery in fine detail, or they can be general or 'holistic' in approach and deal with only the generalised net or overall affects. They can attempt to explain the relationship between all parameters that can be measured and attempt to predict all aspects of the fishery, or they can use only some of the available data to predict only one result such as the net profit. Modelling has been employed to great effect by Somers (1985) to predict the optimum opening date for the Penaeus merguiensis, banana prawn fishery in the Gulf of Carpentaria. Somers (1985) used information on prawn prices and prawn growth rates, together with weekly size surveys, to predict when harvest would maximise the gross profits of prawn fishermen. Sluczanowski (1984) used historical catch data and existing fisheries models to optimise (through modelling) population parameters for the Spencer Gulf prawn fishery of P. latisulcatus, the western king prawn. These parameters were then used in a subsequent model, which had an economic framework, to find management measures which would optimise total industry profits. The deterministic model that will be described below is not as complex as that used by Sluczanowski (1984) in the Spencer Gulf, and as yet has not been elaborated to produce economic parameters other than gross catch values. This model was originally developed to simulate the growth, immigration, emigration and mortality processes of juvenile P. esculentus, brown tiger prawns, in nursery areas of Torres Strait. 1t was then extended to include the adult or commercial phase of the life cycle, and to include the other two commercial species in Torres Strait, Metapenaeus endeavouri, endeavour prawn, and P. longistylus, redspot king prawn. It has already been employed to make crude predictions of the effects of differing seasonal closure periods on prawn catch values. With modification and further sophistication this model can be used to meet many of the prawn fishery managers future needs.

keywords     DP/CU:REPT20:333 shrimp Australia model simulation

abstract
A description of the important commercial prawn fishery in the Torres Strait region of northern Australia. Landing and other statistics described.

keywords     shrimp Australia

abstract
During 1983 research undertaken by the Branch continued to be orientated mainly towards the development requirements of Papua New Guinea's coastal fisheries. Particularly attention has been paid to the need to develop new fishing craft and fishing methods for the artisanal fishery. Two new designs of small craft which have been constructed this year will be fully tested during 1984. Experimental fishing has concentrated on deep-line fishing and results have consistently shown that this method has potential for development in Papua New Guinea (P.N.G.). It is fully recognised that for this research to have any impact on the fishery, it must be demonstrated to the fishermen themselves and two programmes involving local fishing communities have been initiated at Port Moresby and Wewak. Fieldwork on three major projects, a shallow reef study at Kavieng, the Sepik River study and a study of estuarine fish stocks based at Baimuru were completed during 1983 and preliminary analysis has commenced and several reports have been produced. Funds allocated to Research were 30% less than in 1982 and several low priority 'tasks' were not commenced as planned. Since there has not been any major increase in staff numbers, staff shortages have been a major constraint. Research's role in the tuna, prawn and barramundi fisheries has continued to be many that of management, involving the monitoring of catch data. Research into the Torres Strait lobster stocks re-commenced in 1983 with a view to improving our understanding and management of this valuable resource.

keywords     fisheries Papua New Guinea

abstract
In the northern part of the South China Sea the 'big-eye' Priacanthus tayenus, spawned once a year in June, had von Bertalanffy growth parameters of k = 0.8 and Linf = 30 cm, and a mean total annual instantaneous mortality of Z = 2.0, calculated from adjusted catch curves and a mean length equation. The natural mortality rate M = 1.4, fishing mortality rate F = 0.6, and the exploitation rate (E) was 0.27. The maximum potential yield, calculated using Marten's method, was 0.06 kg/recruit when F= 5.4. The fish were heavily parasitised by the protozoan Pleistophora priacanthicola. A second big-eye, P. macracanthus, spawned twice a year in May-June and September, had growth parameters of k=0.7 and Linf = 32, and population parameters of Z =2.0, F=0.7, and E=0.34. The maximum potential yield was 0.13 kg/recruit when F= 5.8. A marked reduction in fishing mortality occurred for both species between 1965 and 1966, coinciding with the onset of the Chinese Cultural Revolution. Our estimates of maximum potential yield correspond to fishing mortalities eight times estimated levels, though such heavy exploitation could risk recruitment failure.

keywords     trawl Hong Kong growth mortality parasitology yield

abstract
Samples of trawl fishes taken from the Gulf of Papua between June and September 1983 were dominated by weight and numbers by sciaenids, engraulids, leiognathids and trichurids. The estimated fish to prawn ratio was 8.8:1. Based on this ratio, the estimated harvest of fishes was 209 kg/hr. If this harvest was extrapolated for all trawl hours for 1982 the estimated total harvest was 11,300 - 17,200t or 1.2 - 1.9t/km2 of trawled grounds. Seasonal and area differences were noted.

keywords     trawl bycatch Papua New Guinea shrimp

abstract
Fishing gears, instrumental to the fishing process, can exert direct impacts on marine communities and habitats. The database described here allows for the analysis of global fishing patterns, by associating all reported global catch with fishing gear types. The fine spatial detail of the Sea Around Us project?s catch database allows for the construction of maps showing subtle changes in the use of fishing gears annually since 1950. Maps included in this report chronicle the expansion of these and other gears in ways that will inform the current debate over their impacts, and provide critical information to shape policy development and management choices.

keywords     fishing gear, database, catch, trawl, dredge, purse seine

abstract
Marine fisheries are the most diverse of the major global food-producing sectors, both in terms of their outputs (species landed1) and the technology used2. One characteristic, however, common to nearly all contemporary fisheries is their dependence on fossil fuels. While numerous analyses have been undertaken to quantify fuel inputs to a wide range of fisheries3,4,5,6,7,8, to date, no attempt has been made to determine the fossil fuel consumption of the world's fishing fleets. Here, we calculate that for 2000, they burned approximately 56.7 billion litres of fuel in the process of landing just over 85 million tonnes of marine fish and invertebrates. Consequently, contemporary fisheries yield approximately 1.77 tonnes of fish per tonne of fuel burned. Moreover, total fuel inputs to the world's fishing fleets account for about 1.4% of total global oil consumption.

keywords     fuel, energy, global fleets

abstract
Alternative fishery management policies under different policy objectives for the 1990s Hong Kong waters ecosystem were explored using a newly developed simulation model named ?policy simulator? under the Ecopath with Ecosim software. Scenarios, which aim to maximize the economic output, the social output, the ecological output, and a compromise between the above three outputs were simulated under different vulnerability settings. Results suggested that policy simulations that aimed to maximize economic and social strategy were sensitive to vulnerability setting. Results from simulations aimed to maximize ecological stability and the compromise scenario are generally consistent between different vulnerabilities, and suggested that fishing effort of all fishing sectors and all except P4/8 fishing sectors, respectively, should be reduced. The study also demonstrated that the economic and social outputs decrease when policy objective focuses increasingly on maximizing ecological stability. The results are consistent with general observations of fisheries management. It is suggested that the ?policy simulator? offers excellent insights into management trade-offs in an ecosystem context.

keywords     model ecosystem policy Hong Kong China

abstract
Fisheries landing statistics from broad statistical reporting areas were mapped as catches with a resolution of 30 minutes of longitude x 30 minutes of latitude. The procedure involved the progressive disaggregation of the statistics, firstly to provide poorly defined records with a better taxonomic identity, and secondly by using a rule-based process involving databases of known distributions of taxa, oceanographic features and of the areas where reporting countries are permitted to fish, in order to spatially disaggregate the data. Maps prepared for reporting years 1950 until 1999 showed trends in the spatial distribution of fisheries catches, provided a valuable means of examining other questions such as interactions between fishing and marine mammals, and provided descriptions of the global catch from large marine ecosystems. Catch maps prepared for the North Atlantic are illustrated and were used in the formation of ecological models and in the preparation of maps of catch value.

keywords     mapping; landings; saup

abstract
This document presents two interrelated studies on the marine fisheries of the People?s Republic of China, both emphasizing, if in different ways, the magnitude of the catches reported throughout the 1990s. The first study, by Lillian Pang and Daniel Pauly, titled ?Chinese Marine Capture Fisheries from 1950 to the late 1990s: the Hopes, the Plans, and the Data,? reviews the history and development of Chinese marine fisheries since 1950, notably the extremely strong increase of reported catches from the mid-1980s on. The case is then made, based on the design of the statistical reporting system, and the professional motivation structure of local fisheries officials, that over-reporting is likely to be the cause for much of the nominal catch increase. Supporting evidence is provided by similar overreporting in other food-producing sectors, by various other fisheries studies (notably of catch per effort trends), the stressed state of Chinese coastal ecosystems, and the proclamation, by China?s Central Government, of a zero-growth policy designed to undermine local over-reporting and to restructure the fisheries sector. The second study, by Reg Watson, titled ?Spatial Allocation of Fisheries Landings from FAO Statistical Areas 61 and 71? describes a rule-based, computer-intensive algorithm developed by the author and associates to map the world?s fisheries catches in ½ degree cells. The resulting global map, which suggests the Chinese shelf and adjacent waters to be as nearly as productive as the Peruvian coastal upwelling system, was broadly reproduced by a General Additive Model that used depth and primary production as predictor variables. The catches reported from Chinese marine waters explained a large fraction of the differences between observed and predicted values, strongly suggesting that current Chinese nominal catches are greatly over-reported. These two studies thus confirm each other, and provide strong evidence that indeed, Chinese national statistics over-report marine catches from Chinese waters. The internal adjustments that correcting for the underlying deficiency of the statistical reporting system will require are not investigated, and nor are the food policy issues implied by these findings. It is clear, however, that these issues are serious, for both China and the rest of the world, thus explaining, if need be, the critical tone of our studies. It is hoped that the Chinese authorities, international bodies, concerned scientists and others will find harmonious ways to resolve these issues.

keywords     landings; China; saup