(BOSTON – April 8, 2019) New research published in the ICES Journal of Marine Science shows that adapting fishing intensity to the health of fish populations is key to making fisheries more climate resilient.
Authored by scientists at the Environmental Defense Fund and University of California Santa Barbara, the study shows that adaptive and responsive strategies for managing fisheries in the face of climate change can help build resilience, resulting in healthier oceans and a more stable supply of fish for people.
Climate change is already putting tremendous pressure on fishing communities around the world, presenting new challenges for fishery scientists and managers. The paper focuses on the use of harvest control rules (HCRs) to set catch limits that are inherently more resilient.
“The right harvest control rule is like adaptive cruise control for your fishery,” said Jake Kritzer, Senior Director with 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.”
Warming waters are causing species of fish to shift their ranges and reproduce at lower rates. Unfortunately, the current system for managing fish catches is often not adaptive enough to respond to these dynamics. In many fisheries, it sets static catch levels at a percentage of the total biomass, and those percentages often don’t change even when the biomass declines.
Adjusting the rate at which fish are allowed to be harvested up and down as the number of fish in the water changes—instead of fishing them at a fixed rate regardless of how the population is doing, builds more resilience into fisheries management and helps optimize the fishery.
“If a catch limit is too high and too many fish are taken out of the ocean, the ecosystem suffers,” said Kritzer. “If a limit is too low, with more fish than can be caught sustainably left in the water, fishermen suffer.”
This new research recommends that managers adopt responsive HCRs that would more rapidly respond to changes in fish populations—as a result of climate change or otherwise.
The approach suggested by Kritzer and his fellow researchers would automatically reduce the catch percentage when managers detect decreases in biomass, and increase it when biomass increases. This enables more immediate responses to effects of climate change and other changing conditions in the ocean, without an immediate scientific evaluation of what caused the changes.
“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.”
Recent science has shown that unfortunately, not all fisheries will be resilient enough to continue supporting fishing in the future. Some stocks are declining in productivity, yield and profits across the board—putting pressure on fishing communities who depend on them for food and livelihoods. These differences underscore the importance of climate vulnerability assessments for harvested species.
“One size fits all does not work when managing for climate change, which means that we need to adjust our management to a more adaptive and resilient approach to buffer against climate change effects,” said Kritzer. “Addressing these new challenges fully could take years, but this paper demonstrates that there are simple steps managers and policymakers can take right now to soften the blow to communities.”
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