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Declines in body size of sockeye salmon associated with increased competition in the ocean

Proceedings of the Royal Society B
By: , , , and 
https://doi.org/10.1098/rspb.2022.2248

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Abstract

Declining body sizes have been documented for several species of Pacific salmon; however, whether size declines are caused mainly by ocean warming or other ecological factors, and whether they result primarily from trends in age at maturation or changing growth rates remain poorly understood. We quantified changes in mean body size and contributions from shifting size-at-age and age structure of mature sockeye salmon returning to Bristol Bay, Alaska, over the past 60 years. Mean length declined by 3%, corresponding to a 10% decline in mean body mass, since the early 1960s, though much of this decline occurred since the early 2000s. Changes in size-at-age were the dominant cause of body size declines and were more consistent than trends in age structure among the major rivers that flow into Bristol Bay. Annual variation in size-at-age was largely explained by competition among Bristol Bay sockeye salmon and interspecific competition with other salmon in the North Pacific Ocean. Warm winters were associated with better growth of sockeye salmon, whereas warm summers were associated with reduced growth. Our findings point to competition at sea as the main driver of sockeye salmon size declines, and emphasize the trade-off between fish abundance and body size.

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Publication type Article
Publication Subtype Journal Article
Title Declines in body size of sockeye salmon associated with increased competition in the ocean
Series title Proceedings of the Royal Society B
DOI 10.1098/rspb.2022.2248
Volume 290
Year Published 2023
Language English
Publisher The Royal Society
Contributing office(s) Northern Rocky Mountain Science Center
Description 20222248, 11 p.
Country United States
State Alaska
Other Geospatial Bristol Bay region
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