Climate change is causing a wide array of physical, chemical, and biological changes in marine ecosystems the world over. As these changes impact on the social and economic viability of fishing communities, they also present new challenges for fishery scientists and managers. Some of the responses to climate change that could lead to more resilient fisheries can be complex, including re-envisioned multinational governance arrangements or complex ecosystem models.
Fortunately, there are responses to climate change that can be simpler to implement. In their recently published paper, “Responsive harvest control rules provide inherent resilience to adverse effects of climate change and scientific uncertainty", Kritzer and his co-authors consider how climate impacts influence the most effective harvest control rules (HCRs) to adopt for different stocks. An HCR generally determines the target fishing mortality rate as a function of estimated biomass and is, arguably, where science most directly confronts policy in fisheries management. The form of an HCR reflects the objectives and risk tolerance for the fishery, as well as the productivity of the stock and degree of scientific uncertainty.
Often, fisheries can meet management objectives by managing to a fixed but risk-averse level of fishing mortality, such as some level below the fishing mortality rate expected to produce maximum sustainable yield (FMSY). The authors support this approach for those stocks expected to benefit from the effects of climate change or experience negligible effects. However, for those stocks that are expected to suffer adversely from the effects of climate change, a different approach is warranted.
Specifically, the authors point to an HCR that adjusts the target fishing mortality rate upward and downward with measured changes in biomass to dampen the negative impacts on biomass, yield, and profits. Importantly, this benefit was realized despite the HCR not explicitly accounting for effects of climate change on productivity and reference points.
When stock dynamics are changing in directional but uncertain ways, carefully tracking its state and responding regularly can be an effective management strategy while science works to untangle the new productivity regime.
Lobster boat, Maine. Will the American lobster stock in the Gulf of Maine improve growth as a consequence of climate change? Photo: Jake Kritzer.
Paper title: Responsive
harvest control rules provide inherent resilience to adverse effects of climate
change and scientific uncertainty
Authors: Jake P. Kritzer, Chris Costello, Tracey Mangin, Sarah L. Smith