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Climate Change May Cause Shifts in Growth and Instantaneous Natural Mortality of American Shad Throughout Their Native Range
Author(s) -
GilliganLunda Erin K.,
Stich Daniel S.,
Mills Katherine E.,
Bailey Michael M.,
Zydlewski Joseph D.
Publication year - 2021
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1002/tafs.10299
Subject(s) - alosa , climate change , stock (firearms) , population , stock assessment , environmental science , population growth , range (aeronautics) , population model , fish migration , maximum sustainable yield , fishery , ecology , geography , fisheries management , biology , fish <actinopterygii> , fishing , demography , archaeology , sociology , composite material , materials science
American Shad Alosa sapidissima is an anadromous species with populations ranging along the U.S. Atlantic coast. Past American Shad stock assessments have been data limited and estimating system‐specific growth parameters or instantaneous natural mortality ( M ) was not possible. This precluded system‐specific stock assessment and management due to reliance on these parameters for estimating other population dynamics (such as yield per recruit). Furthermore, climate‐informed biological reference points remain a largely unaddressed need in American Shad stock assessment. Population abundance estimates of American Shad and other species often rely heavily on M derived from von Bertalanffy growth function (VBGF) parameters. Therefore, we developed Bayesian hierarchical models to estimate coastwide, regional, and system‐specific VBGF parameters and M using data collected from 1982 to 2017. We tested predictive performance of models that included effects of various climate variables on VBGF parameters within these models. System‐specific models were better supported than regional or coast‐wide models. Mean asymptotic length ( L ∞ ) decreased with increasing mean annual sea surface temperature (SST) and degree days (DD) experienced by fish during their lifetime. Although uncertain, K (Brody growth coefficient) decreased over the same range of lifetime SST and DD. Assuming no adaptation, we projected changes in VBGF parameters and M through 2099 using modeled SST from two climate projection scenarios (Representative Concentration Pathways 4.5 and 8.5). We predicted reduced growth under both scenarios, and M was projected to increase by about 0.10. It is unclear how reduced growth and increased mortality may influence population productivity or life history adaptation in the future, but our results may inform stock assessment models to assess those trade‐offs.