Abstract
Rebuilding depleted fish stocks is an international policy goal and a 2020 Aichi target under the Convention on Biological Diversity. However, stock productivity may shift with future climate change, with unknown consequences for sustainable harvesting, biomass targets and recovery timelines. Here we develop a stochastic modelling framework to characterize variability in the intrinsic productivity parameter (r) and carrying capacity (K) for 276 global fish stocks worldwide. We use models of dynamic stock productivity fitted via Bayesian inference to forecast rebuilding timelines for depleted stocks. In scenarios without fishing, recovery probabilities are reduced by 19%, on average, relative to models assuming static productivity. Fishing at 90% of the maximum sustainable rate depresses recovery probabilities by 42%, on average, relative to static models. This work reveals how a changing environmental context can delay the rebuilding of depleted fish stocks, and provides a framework to account for the potential impacts of environmental change on the productivity of wildlife populations more broadly.
Highlights
Rebuilding depleted fish stocks is an international policy goal and a 2020 Aichi target under the Convention on Biological Diversity
There is an increasing recognition that ongoing environmental change is already having an impact on fish population dynamics[10,11,12,13,14] and that recovery targets and timelines may be moving targets
This challenges the commonly held assumption that populations are in a long-term steady state[15], wherein the production of biomass varies interannually but is governed by biological parameters that are stationary over time. While this assumption may have been questionable a priori, recent empirical analyses of global fisheries time series have suggested that significant non-stationary behaviour is occurring in the majority of global fish stocks in response to environmental change[13], while persistent regime-like behaviour[14] can cause unexpected collapse of otherwise tightly controlled populations[16]
Summary
Rebuilding depleted fish stocks is an international policy goal and a 2020 Aichi target under the Convention on Biological Diversity. There is an increasing recognition that ongoing environmental change is already having an impact on fish population dynamics[10,11,12,13,14] and that recovery targets and timelines may be moving targets This challenges the commonly held assumption that populations are in a long-term steady state[15], wherein the production of biomass varies interannually but is governed by biological parameters that are stationary over time. While this assumption may have been questionable a priori, recent empirical analyses of global fisheries time series have suggested that significant non-stationary behaviour is occurring in the majority of global fish stocks in response to environmental change[13], while persistent regime-like behaviour[14] can cause unexpected collapse of otherwise tightly controlled populations[16]. We further demonstrate how recovery targets and timelines must be adapted to account for the effects of environmental change today and into the future
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