Written by Nereus Fellow Kisei Tanaka,
Understanding the biogeography of species targeted by fisheries is important to keep stock assessments relevant in a world where climate changes. The paper recently accepted by the ICES Journal of Marine Science by the Tanaka et al. is contributing to including environmental factors into the assessment of climatically-influenced commercial fisheries.
The American lobster, one of the most iconic modern American fishery stocks, represents one of the largest and most valuable fisheries in the northern hemisphere, with total U.S. landings steadily increasing over the past 35 years. Studies suggest the US lobster landing is driven by changes in climate-sensitive lobster recruitment, and warming temperatures may have contributed to an increase in recruitment over the past decade. The US lobster fishery has recognized the need to better understand the factors leading to recruitment changes. However, much like the regulation of most industrial fisheries, assessment of US lobster stocks is still exclusively based on the analysis of harvest rates and abundance estimates from previous years.
In this paper, Tanaka et al. developed a model-based approach to incorporate environmental viability products into single-species stock assessments.
They used the bioclimate envelope model to hindcast temporal variability in lobster recruitment habitat suitability index using bottom temperature and salinity. They also used the climate-driven habitat suitability index to inform the lobster recruitment dynamics within the size-structured population dynamics model. The authors compare estimated recruitment and fishing mortality between fits of the assessment model with and without the environmental index and calculate the retrospective bias (Mohn’s Rho) for the two models. Based on these comparisons, the authors conclude that climate-driven changes in lobster habitat suitability contributed to increased recruitment and presents a potential improvement to population assessment.
The practice of incorporating environmental variability into fishery stock assessment is still limited to a few regions. Meanwhile, the failure to incorporate environmental information into management has been implicated in past fisheries collapses. Climate-driven shifts in the distribution and productivity of marine species adds urgency to addressing this omission. This study presents a model-based approach that can be used to improve our understanding of environmental-driven marine ecological processes and enhance our adaptive management capacity in a changing environment.