With a growing consensus that climate change is causing drastic transformations of marine ecosystems and fish stock dynamics, two recent studies have addressed the importance of taking a more adaptive and responsive approach to their management.
The first study, published in the ICES Journal of Marine Science, shows that adjusting fishing levels when fish populations change is key to making global fisheries more climate-resilient. The result of making this shift would be healthier oceans and a more stable supply of fish for consumption, according to scientists at the Environmental Defense Fund and the University of California, Santa Barbara.
Their paper outlines the fact that many commercially important fish stocks are vulnerable to the effects of climate change, and that managing those stocks sustainably in the future will be a large and growing challenge for fisheries scientists and managers. The paper recommends responsive harvest control rules (HCRs) that automatically reduce catch percentages when decreases in biomass are detected, and increases when biomass increases. By adopting HCRs, “inherent resilience” could be introduced into the system, reducing the adverse effects of climate change while longer-term solutions are sought to better address the negative impacts of global warming.
“Using the right harvest-control rule is like having adaptive cruise control for your fishery,” said Jake Kritzer, a senior director of Environmental Defense Fund’s Oceans program and lead author of the paper. “When you need to slow down, the system can automatically adjust to the right level. Then, when the road ahead is clear, it allows you to return to a higher level.”
Warmer waters caused by climate change are resulting in lower reproduction rates in fish and forcing them to migrate out of their natural ranges. The current system for managing fish catches is often not adaptive enough to respond to these dynamics, the report noted. In addition, current catch levels are being calculated on biomass that may be incorrect as a result of these large-scale changes, the report found.
“There’s a lot we do not know about how fisheries will respond to climate change, but using HCRs, where science and policy most directly meet, tells us a lot more about how healthy fish populations are, enabling us to respond to changes on the water,” Kritzer said. “Addressing these new challenges fully could take years, but we have shown that there are simple steps managers and policymakers can take right now to soften the blow to communities.”
The second study, part of the Lenfest Ocean Program, which focuses on the environmental, economic, and social impacts of fishing, fisheries management, and aquaculture, is just getting underway and will continue through 2021.
Led by Andrew Pershing, who is collaborating with colleagues Lisa Kerr and Jonathan Labaree at the Gulf of Maine Research Institute (GMRI), the study will review how different regions and countries are responding to shifting fish populations. The results of their research will be used to develop guidance for fisheries management authorities in the U.S. Northeast and Mid-Atlantic.
An important, but previously little-studied consequence of shifting fish populations is the issue of who is allowed to catch fish that have migrated to new locations, Pershing, Kerr, and Labaree said. This question poses the challenge of deciding whether it is more reasonable to preserve the access rights and livelihoods of fishermen who currently target the population, or whether it is more fair to reallocate access to those who operate nearer to the new location, where the fishery might be more economically efficient.
For example, the Atlantic States Marine Fisheries Commission allocates a fixed proportion of the total allowable summer flounder catch to each state, but allows fishermen to travel to catch the species as it shifts, provided they bring it to port in their home states. In contrast, U.S. and Canadian managers reallocate Georges Bank haddock between the two countries to align with shifting stock distribution, but do not let fishermen cross the international boundary to fish.
The research team aims to characterize and categorize the different types of allocation systems used in fisheries and policy contexts all around the world, and to compare the experiences of adapting to shifting stocks. This will allow them to draw up a range of options for adaptation and provide guidance on the benefits and challenges of each.
Results will be shared in focus groups with fishery stakeholders, who will help to inform the range of options for adapting to shifting fish stocks.
“Climate change is causing fish to move across the map. Our goal is to develop alternatives for how fisheries could adjust to shifts that are already underway,” Pershing said.
