Egg retention of high-latitude sockeye salmon (Oncorhynchus nerka) in the Pilgrim River, Alaska, during the Pacific marine heatwave of 2014–2016

Polar Biology
By: , and 

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Abstract

Ocean and freshwater conditions can influence spawning success of Pacific salmon (Oncorhynchus spp.) by governing the energy content of fish at the start of and during the spawning migration. Ocean conditions determine the energy stores of fish at the freshwater entry, while freshwater conditions determine how quickly stored energy is depleted as individuals migrate to spawning grounds in natal rivers and lakes. We assessed the occurrence of sockeye salmon (Oncorhynchus nerka) egg retention (failure to deposit eggs) in a high-latitude (~ 65°N) watershed that has a large, inter-annual variation in the number of returning adults. We also explored relationships between ocean and freshwater conditions with egg retention of female sockeye salmon. The proportion of females with egg retention (> 50 eggs) varied by threefold (12 to 36%) across years (2013 to 2020) and was related to ocean conditions represented by the North Pacific Index (NPI). Egg retention was more common in years with low NPI values (a stronger Aleutian Low) in association with the Pacific marine heatwave of 2014–2016 that disrupted food webs. This initial study contains the first empirical data observing the influence of ocean conditions on egg retention for any Pacific salmon population. The lack of any relationship between egg retention and freshwater temperatures was consistent with water temperatures primarily occurring below thresholds associated with heat stress related mortality (< 18 °C). Understanding the amount of egg retention and how environmental drivers influence egg retention within Pacific salmon populations provides insights for managers assessing the number of successful spawners and helps refine escapement-based management efforts.

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Publication type Article
Publication Subtype Journal Article
Title Egg retention of high-latitude sockeye salmon (Oncorhynchus nerka) in the Pilgrim River, Alaska, during the Pacific marine heatwave of 2014–2016
Series title Polar Biology
DOI 10.1007/s00300-021-02902-8
Volume 44
Year Published 2021
Language English
Publisher Springer
Contributing office(s) Alaska Science Center Water
Description 12 p.
First page 1643
Last page 1654
Country United States
State Alaska
Other Geospatial Pilgrim River
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