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MEPS 635:169-185 (2020)  -  DOI: https://doi.org/10.3354/meps13213

Estimating synchronous changes in condition and density in eastern Bering Sea fishes

Arnaud Grüss1,*, Jin Gao2, James T. Thorson3, Christopher N. Rooper4, Grant Thompson5, Jennifer L. Boldt4, Robert Lauth6

1School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98105-5020, USA
2Centre for Fisheries Ecosystem Research, Fisheries and Marine Institute of Memorial University of Newfoundland, 155 Ridge Rd, St. John’s, NL A1C 5R3, Canada
3Habitat and Ecological Process Research Program, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115, USA
4Fisheries and Oceans Canada, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, BC V9T 6N7, Canada
5Resource Ecology and Fisheries Management Division, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115, USA
6Resource Assessment and Conservation Engineering Division, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, 7600 Sand Point Way NE, Seattle, WA 98115, USA
*Corresponding author:

ABSTRACT: Estimating fish condition, the relative weight of an individual fish given its body length, is a convenient way to relate the physiological health and energetic status of fishes to their productivity. Despite evidence of density-dependence effects on condition in some species, previous research has not jointly estimated synchronous changes in condition and density operating at fine spatial scales (a few km). Therefore, we developed a spatio-temporal modeling approach that simultaneously estimates correlated variation in density (measured as numbers per area) and condition. We applied our approach to 6 eastern Bering Sea (EBS) groundfish species (4 flatfishes and 2 gadoids) for the period 1992-2016, and estimated correlations in spatial variation (unmeasured variation that is stable over time) and spatio-temporal variation (unmeasured variation that changes between years). Spatial variation in density had a strong significant negative association with spatial variation in condition for 3 flatfishes and a positive association for one gadoid. Spatio-temporal variation in density had a significant association with spatio-temporal variation in condition for one flatfish (negative) and one gadoid (positive). Moreover, for the 6 study species, bottom temperature was identified as an important predictor of both density and condition. The increasing trend in bottom temperatures between 1992 and 2016 was accompanied by an overall increase in the abundance-weighted condition of 5 species. We conclude that forecasts of changes in weight-at-age within some EBS groundfish assessments will require an understanding of both density-dependence and bottom temperature effects on fish condition to better prepare for future climate and exploitation changes.


KEY WORDS: Condition · Le Cren’s relative condition index · Density-dependence · Spatiotemporal models · Groundfishes · Eastern Bering Sea · Bottom temperature effects


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Cite this article as: Grüss A, Gao J, Thorson JT, Rooper CN, Thompson G, Boldt JL, Lauth R (2020) Estimating synchronous changes in condition and density in eastern Bering Sea fishes. Mar Ecol Prog Ser 635:169-185. https://doi.org/10.3354/meps13213

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