Cody Szuwalski

Global fishery prospects under contrasting management regimes

Significance What would extensive fishery reform look like? In addition, what would be the benefits and trade-offs of implementing alternative approaches to fisheries management on a worldwide scale? To find out, we assembled the largest-of-its-kind database and coupled it to state-of-the-art bioeconomic models for more than 4,500 fisheries around the world. We find that, in nearly every country of the world, fishery recovery would simultaneously drive increases in food provision, fishery profits, and fish biomass in the sea. Our results suggest that a suite of approaches providing individual or communal access rights to fishery resources can align incentives across profit, food, and conservation so that few trade-offs will have to be made across these objectives in selecting effective policy interventions. 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,

High fishery catches through trophic cascades in China

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.

Environment drives forage fish productivity.

Significance Fishing marine ecosystems indiscriminately and intensely can have negative impacts on biodiversity, but it may increase the biomass of fish available for capture in the system. We explore the possibility that China’s high fishery catches are a result of predator removal using an ecosystem model of the East China Sea (ECS). We show that China’s high fishery catches can be explained by the removal of larger predatory fish and consequent increases in the production of smaller fish. We project that single-species management would decrease catches in the ECS by reversing these ecosystem effects. Fisheries similar to those in China produce a large fraction of global catch; management reform in these areas must consider the entire ecosystem, rather than individual species. 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.

Production is a poor metric for identifying regime-like behavior in marine stocks

Understanding the interaction between fishing and natural variations in productivity is a central question in fisheries management. Essington et al. (1) advance the discussion on drivers of forage fish dynamics by highlighting the role of natural decreases in biomass collapses. A key conclusion of their work is that fishing increases the magnitude and frequency of collapse in biomass. More intense fishing necessarily results in fewer fish; however, the higher exploitation rates commonly seen as forage fish biomass declines do not always mean that fishing precipitated collapses in productivity.

An Evaluation of Harvest Control Methods for Fishery Management

Vert-pre et al. (1) identified regimes in productivity for marine fish stocks, with the goal of urging management to develop strategies that are robust to regime-like behavior. Identification of drivers of productivity [i.e., is the stock driven by spawning biomass (the abundance hypothesis in Vert-pre et al.’s analysis in ref. 1) or environment (the regimes, random, and mixed hypotheses)?] is key to selecting management strategies. Management strategies that are robust to regime-like behavior (e.g., constant F or shifting target biomasses) can be more risky for spawning biomass-driven stocks. Therefore, to be useful to management, the presented methods must identify the drivers of productivity for individual …

Changing fisheries productivity and food security

ABSTRACT Fisheries managers seek to maintain sustainable fisheries production, but successful management often requires the pursuit of multiple biological, ecological, and socioeconomic objectives simultaneously. Fisheries managers must choose among a broad range of harvest control methods (HCMs) to meet management objectives. This review identifies strengths and weaknesses of eight HCMs and evaluates their ability to meet a multitude of common biological, ecological, and socioeconomic management objectives such as protecting spawning biomass, reducing bycatch, and sustaining fishers’ profit. Evidence suggests that individual HCMs often fail to meet management objectives and may unintentionally create incentives to race to fish, discard catch and overcapitalize fishing operations. These limitations can be overcome by strategically combining multiple controls or incorporating rights-based and spatial management.

Reducing retrospective patterns in stock assessment and impacts on management performance

Understanding changes in productivity for populations of exploited marine fish is important for appropriate management and conservation. Britten et al. (1) show that, on average, the productivity of fish stocks have declined 3% per decade. This figure was an unweighted mean, and therefore gave equal weight to all stocks, regardless of size. An unweighted mean is a useful measure of changing productivity, particularly when considering conservation of individual stocks. However, food security is a central concern for many countries bordering the ocean, so we should also ask, “How can changes in productivity influence the total biomass in the ocean and the total catch derived from that biomass?”

Examining common assumptions about recruitment: a meta-analysis of recruitment dynamics for worldwide marine fisheries

Reducing retrospective patterns in stock assessment and impacts on management performance Cody S. Szuwalski,* James N. Ianelli, and André E. Punt Bren School of Environmental Science and Management, Marine Science Institute, University of California, Santa Barbara, CA 93106, USA National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Centre, 7600 Sand point Way NE, Seattle, WA 98115, USA School of Aquatic and Fishery Sciences, University of Washington, 1122 Boat Street, Seattle, WA 98195, USA