Marine fish stocks are an important part of the world food system and are particularly important for many of the poorest people of the world. Most existing analyses suggest overfishing is increasing, ...and there is widespread concern that fish stocks are decreasing throughout most of the world. We assembled trends in abundance and harvest rate of stocks that are scientifically assessed, constituting half of the reported global marine fish catch. For these stocks, on average, abundance is increasing and is at proposed target levels. Compared with regions that are intensively managed, regions with less-developed fisheries management have, on average, 3-fold greater harvest rates and half the abundance as assessed stocks. Available evidence suggests that the regions without assessments of abundance have little fisheries management, and stocks are in poor shape. Increased application of area-appropriate fisheries science recommendations and management tools are still needed for sustaining fisheries in places where they are lacking.
Data from 4,713 fisheries worldwide, representing 78% of global reported fish catch, are analyzed to estimate the status, trends, and benefits of alternative approaches to recovering depleted ...fisheries. For each fishery, we estimate current biological status and forecast the impacts of contrasting management regimes on catch, profit, and biomass of fish in the sea. We estimate unique recovery targets and trajectories for each fishery, calculate the year-by-year effects of alternative recovery approaches, and model how alternative institutional reforms affect recovery outcomes. Current status is highly heterogeneous—the median fishery is in poor health (overfished,with further overfishing occurring), although 32% of fisheries are in good biological, although not necessarily economic, condition. Our business-as-usual scenario projects further divergence and continued collapse for many of the world’s fisheries. Applying sound management reforms to global fisheries in our dataset could generate annual increases exceeding 16 million metric tons (MMT) in catch, $53 billion in profit, and 619 MMT in biomass relative to business as usual. We also find that, with appropriate reforms, recovery can happen quickly, with the median fishery taking under 10 y to reach recovery targets. Our results show that commonsense reforms to fishery management would dramatically improve overall fish abundance while increasing food security and profits.
High fishery catches through trophic cascades in China Szuwalski, Cody S.; Burgess, Matthew G.; Costello, Christopher ...
Proceedings of the National Academy of Sciences - PNAS,
01/2017, Letnik:
114, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Indiscriminate and intense fishing has occurred in many marine ecosystems around the world. Although this practice may have negative effects on biodiversity and populations of individual species, it ...may also increase total fishery productivity by removing predatory fish. We examine the potential for this phenomenon to explain the high reported wild catches in the East China Sea—one of the most productive ecosystems in the world that has also had its catch reporting accuracy and fishery management questioned. We show that reported catches can be approximated using an ecosystem model that allows for trophic cascades (i.e., the depletion of predators and consequent increases in production of their prey). This would be the world’s largest known example of marine ecosystem “engineering” and suggests that trade-offs between conservation and food production exist. We project that fishing practices could be modified to increase total catches, revenue, and biomass in the East China Sea, but single-species management would decrease both catches and revenue by reversing the trophic cascades. Our results suggest that implementing single-species management in currently lightly managed and highly exploited multispecies fisheries (which account for a large fraction of global fish catch) may result in decreases in global catch. Efforts to reform management in these fisheries will need to consider system wide impacts of changes in management, rather than focusing only on individual species.
Assumptions about the future productivity of a stock are necessary to calculate sustainable catches in fisheries management. Fisheries scientists often assume the number of young fish entering a ...population (recruitment) is related to the biomass of spawning adults and that recruitment dynamics do not change over time. Thus, managers often use a target biomass based on spawning biomass as the basis for calculating sustainable catches. However, we show recruitment and spawning biomass are not positively related over the observed range of stock sizes for 61% of 224 stocks in the RAM Legacy Stock Assessment Database. Furthermore, 85% of stocks for which spawning biomass may not drive recruitment dynamics over the observed ranges exhibit shifts in average recruitment, which is often used in proxies for target biomasses. Our results suggest that the environment more strongly influences recruitment than spawning biomass over the observed stock sizes for many stocks. Management often endeavours to maintain stock sizes within the observed ranges, so methods for setting management targets that include changes within an ecosystem may better define the status of some stocks, particularly as climate changes.
Abstract The potential influence of climate change on the future distribution and abundance of fish (and therefore commercial fisheries and food security) is increasingly recognized in the fishery ...management community. A changing climate will likely have differing effects on different species; some will flourish, some will flounder. Management targets for fishing mortality and spawning biomass are often calculated by assuming stationary population processes, but under climate change, this assumption may be violated. Non-stationary population processes can introduce bias into estimates of biomass from stock assessments and calculations of target fishing mortalities and biomasses. However, few accepted frameworks exist for incorporating the changing influence of the environment on exploited populations into management strategies. Identifying changes in population processes due to environmental influences is important in order to enable climate-enhanced management strategy evaluations to elucidate the potential benefits and costs of changing management targets. Cost/benefit analyses will also be useful when coincidentally caught species respond differently to environmental change.
The collapse of eastern Bering Sea snow crab Szuwalski, Cody S.; Aydin, Kerim; Fedewa, Erin J. ...
Science (American Association for the Advancement of Science),
10/2023, Letnik:
382, Številka:
6668
Journal Article
Recenzirano
The snow crab is an iconic species in the Bering Sea that supports an economically important fishery and undergoes extensive monitoring and management. Since 2018, more than 10 billion snow crab have ...disappeared from the eastern Bering Sea, and the population collapsed to historical lows in 2021. We link this collapse to a marine heatwave in the eastern Bering Sea during 2018 and 2019. Calculated caloric requirements, reduced spatial distribution, and observed body conditions suggest that starvation played a role in the collapse. The mortality event appears to be one of the largest reported losses of motile marine macrofauna to marine heatwaves globally.
Editor’s summary
Marine heatwaves, a component of our impact on the Earth’s climate, can bring both expected and unexpected environmental change. Between 2018 and 2021, after a period of historically high crab abundance and a series of marine heatwaves, the population of snow crab in the Bering Sea declined by 10 billion. Szuwalksi
et al
. used survey data to model the potential drivers of the decline in this ecologically and commercially important species. They found that the temperature of the water was not above the species’ thermal limits, but it did increase their caloric needs considerably (see the Perspective by Kruse). This increase, in conjunction with a restriction in range, led to an unexpected mass starvation event. —SNV
A marine heatwave precipitated the collapse of the eastern Bering Sea snow crab population.
Abstract Fishing behavior is an important link between management decisions and bioeconomic outcomes. The diversity in fishers’ behavior, motivations, and abilities should inform incentive structures ...if management aims to consider heterogeneous impacts on and by communities. Modeling human behavior in resource management is important for successful fisheries, especially for fisheries undergoing rapid transformation, such as the Alaskan snow crab fishery. This study modeled how snow crabbers choose where to fish in the eastern Bering Sea and examined the diversity of strategies among individuals by fitting a random utility model to data on fishing locations using a variety of potential drivers of behavior as covariates. The overall fishing strategy of the snow crab fleet prioritizes revenue and shared information, while avoiding risk, poor weather, and cost. Diversity of fishing strategies was driven by differences in spatial footprint, vessel size, and ports of landing. Larger vessels ventured farther north, where weather conditions are more extreme. Despite differences in vessel size, crabbers were spatially adaptive and switched fishing regions depending on the abundance and distribution of crab. These findings on the patterns of fishing strategies can inform better management of the Alaskan snow crab fishery as it undergoes rebuilding.
Environment drives forage fish productivity Szuwalski, Cody S.; Hilborn, Ray
Proceedings of the National Academy of Sciences - PNAS,
06/2015, Letnik:
112, Številka:
26
Journal Article
Abstract A recent population collapse of eastern Bering Sea (EBS) snow crab (Chionoecetes opilio) led to the first-ever closure of the snow crab fishery in 2022. The population collapse, caused, in ...part, by unprecedented warming, was preceded by peaks in juvenile snow crab density (2018) and bitter crab disease (BCD, Hematodinium sp.; 2016), a fatal crustacean disease. Annual bottom trawl surveys in the EBS show high year-to-year spatiotemporal variation in BCD-infected crab, yet it remains unclear what ecological drivers might explain the variation. We used statistical models of BCD presence/absence to examine the relative importance of intrinsic and extrinsic factors as drivers of BCD. We found a dome-shaped relationship between temperature and BCD presence, and results suggest that 2–4°C bottom temperatures are more likely to support BCD. Matching with past work across the globe, we find that stations with high population density of small, new shell crab are most likely to be BCD-positive. While our work highlights the challenges of disease monitoring in the EBS, our results indicate that indirect management measures related to snow crab rebuilding and recruitment may be more appropriate than directed fisheries management in mitigating BCD impacts.
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