Rebuilding global fisheries under uncertainty

Memarzadeh, Milad; Britten, Gregory L.; Worm, Boris; Boettiger, Carl

doi:10.1073/pnas.1902657116

Cited by 41 publications

(33 citation statements)

References 30 publications

(38 reference statements)

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“…Over-exploitation threatens the ecological sustainability of many of the world’s fisheries [ 2 ]. Ecological models aim to understand the incentives and consequences of overfishing, and suggest ecologically enlightened management strategies [ 31 , 32 ]. This may not be enough.…”

Section: Discussionmentioning

confidence: 99%

Fisheries management as a Stackelberg Evolutionary Game: Finding an evolutionarily enlightened strategy

et al. 2021

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Fish populations subject to heavy exploitation are expected to evolve over time smaller average body sizes. We introduce Stackelberg evolutionary game theory to show how fisheries management should be adjusted to mitigate the potential negative effects of such evolutionary changes. We present the game of a fisheries manager versus a fish population, where the former adjusts the harvesting rate and the net size to maximize profit, while the latter responds by evolving the size at maturation to maximize the fitness. We analyze three strategies: i) ecologically enlightened (leading to a Nash equilibrium in game-theoretic terms); ii) evolutionarily enlightened (leading to a Stackelberg equilibrium) and iii) domestication (leading to team optimum) and the corresponding outcomes for both the fisheries manager and the fish. Domestication results in the largest size for the fish and the highest profit for the manager. With the Nash approach the manager tends to adopt a high harvesting rate and a small net size that eventually leads to smaller fish. With the Stackelberg approach the manager selects a bigger net size and scales back the harvesting rate, which lead to a bigger fish size and a higher profit. Overall, our results encourage managers to take the fish evolutionary dynamics into account. Moreover, we advocate for the use of Stackelberg evolutionary game theory as a tool for providing insights into the eco-evolutionary consequences of exploiting evolving resources.

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Section: Discussionmentioning

confidence: 99%

Fisheries management as a Stackelberg Evolutionary Game: Finding an evolutionarily enlightened strategy

et al. 2021

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“…If we are to achieve internationally agreed conservation targets such as Sustainable Development Goal 14 (UN 2015) and Aichi Biodiversity Target 6 (CBD 2010), we must account for various sources of uncertainty to assess overexploitation risk (Regan et al . 2005; Memarzadeh & Boettiger 2018) and recovery potential (Memarzadeh et al . 2019) and set conservation priorities.…”

Section: Introductionmentioning

confidence: 99%

Shaping sustainable harvest boundaries for marine populations despite estimation bias

Goto¹,

Devine²,

Umar³

et al. 2020

Preprint

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Imperfect knowledge of social–ecological systems can obscure predictability of resource fluctuation and, in turn, lead to erroneous risk assessments and delayed management actions. Systematic error in population status such as persistent overestimation of abundance is a pervasive conservation problem and has plagued assessments of commercial exploitation of marine species, threatening its sustainability.Using North Sea saithe (Pollachius virens)–a demersal (bottom-water) predatory fish–as a real-world case study, we illustrate a precautionary approach to diagnose robustness of harvest rules to persistent estimation bias (overestimated stock abundance and underestimated fishing mortality rate) and to develop alternative protective measures that minimize population depletion (quasi-extinction) risk by propagating known sources of uncertainty (process, observation, and implementation) through closed-loop simulation of resource–management feedback systems (management strategy evaluation, MSE).Analyses showed that the harvest rules set for saithe are robust to a moderate amount (10– 30%) of estimation bias. More severe bias sets overly optimistic catch limits and promotes overexploitation only in the short term; unacceptably high quasi-extinction risks, however, result primarily from progressively amplified amplitudes of catch fluctuation. Although these undesirable outcomes were, to some extent, mitigated by applying a policy tool to suppress catch fluctuation, this tool falls short of being an effective measure to achieve management goals.More consistent performance of management measures was achieved by developing and applying more precautionary harvest rules through MSE by explicitly accounting for bias. When bias became more severe, raising threshold abundance (by 8–24%) that triggers management actions and lowering target exploitation rate (by 6–29%) would not only safeguard against overexploitation and depletion but also provide catch stability (less disruption in fishing operations).We show that the precautionary approach to risk management through MSE offers a powerful tool to set safe harvest boundaries when assessments are persistently biased. Given challenges in identifying the sources, we suggest bias be routinely evaluated through MSE, and alternative measures be developed to set catch limits when needed. By explicitly accounting for key sources of uncertainty in managing commercial exploitation, our proposed approach ensures effective conservation and sustainable exploitation of living marine resources even under profound uncertainty.

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“…A growing body of literature highlights the effects of climate on fish populations (3) in the context of warming waters (2, 4–6) and interannual variability (7). Models show that failure to account for climate and other forms of uncertainty can exacerbate the pressure stocks face from fishing and ultimately lead to stock collapse (8, 9). This highlights the need for better empirical understanding of climate’s impact on fisheries and the communities that depend on them.…”

mentioning

confidence: 99%

“…If natural mortality is greater than managers anticipate or fish productivity is lower than expected, it can lead to quotas that are unintentionally set too high and consequently to overfishing (2). Theoretical models suggest that fishing practices that fail to account for climate impacts on productivity can lead to suboptimal economic harvest, resource rent declines, and even potential collapse (8, 9).…”

mentioning

confidence: 99%

Climate variability reduces employment in New England fisheries

Oremus

2019

Proc. Natl. Acad. Sci. U.S.A.

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Climate change is already affecting fish productivity and distributions worldwide, yet its impact on fishing labor has not been examined. Here I directly link large-scale climate variability with fishery employment by studying the effects of sea-surface pressure changes in the North Atlantic region, whose waters are among the world’s fastest warming. I find that climate shocks reduce not only regional catch and revenue in the New England fishing sector, but also ultimately county-level wages and employment among commercial harvesters. Each SD increase from the climatic mean decreases county-level fishing employment by 13%, on average. The South Atlantic region serves as a control due to its different ecological response to climate. Overall, I estimate that climate variability from 1996 to 2017 is responsible for a 16% (95% CI: 10% to 22%) decline in county-level fishing employment in New England, beyond the changes in employment attributable to management or other factors. This quantitative evidence linking climate variability and fishing labor has important implications for management in New England, which employs 20% of US commercial harvesters. Because the results are mediated by the local biology and institutions, they cannot be directly extrapolated to other regions. But they show that climate can impact fishing outcomes in ways unaccounted by management and offer a template for study of this relationship in fisheries around the world.

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Rebuilding global fisheries under uncertainty

Cited by 41 publications

References 30 publications

Fisheries management as a Stackelberg Evolutionary Game: Finding an evolutionarily enlightened strategy

Fisheries management as a Stackelberg Evolutionary Game: Finding an evolutionarily enlightened strategy

Shaping sustainable harvest boundaries for marine populations despite estimation bias

Climate variability reduces employment in New England fisheries

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