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Marine Ecology Progress Series

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MEPS 640:147-169 (2020)  -  DOI:

Variable prey consumption leads to distinct regional differences in Chinook salmon growth during the early marine critical period

Melanie J. Davis1,4,*, Joshua W. Chamberlin2, Jennifer R. Gardner1, Kristin A. Connelly1,5, Madilyn M. Gamble1,6, Brian R. Beckman2, David A. Beauchamp3

1School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98105, USA
2Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, Seattle, Washington 98112, USA
3Western Fisheries Research Center, US Geological Survey, Seattle, Washington 98115, USA
4Present address: Western Ecological Research Center, Olympia Substation, US Geological Survey, Olympia, Washington 98516, USA
5Present address: School of the Environment, Washington State University Vancouver, Vancouver, Washington 98686, USA
6Present address: Graduate Program in Ecology, Evolution, Ecosystems, and Society, Dartmouth College, Hanover, New Hampshire 03755, USA
*Corresponding author:

ABSTRACT: Growth during the early marine critical period is positively associated with survival and recruitment for Pacific salmon Oncorhynchus spp., so it is important to understand how certain foraging strategies may bolster growth in estuarine and marine environments. To elucidate how spatiotemporal and demographic differences in diet contribute to growth rate variability, we analyzed stomach contents in tandem with morphometric and hormonal indices of growth for subyearling Chinook salmon O. tshawytscha captured in Puget Sound, Washington, USA. Regional dietary patterns indicated that fish caught in northern Puget Sound ate insects in the estuarine and nearshore habitats, followed by decapod larvae, euphausiids, or forage fish in the offshore zone. In southern Puget Sound, fish ate insects in the estuary but were more likely to eat mysids and other crustaceans in the nearshore zone. In the marine habitats adjacent to the San Juan Islands, subyearlings ate forage fish, and their stomachs were as much as 1.4 to 3 times fuller than salmon captured in other regions. Scale-derived growth rates and insulin-like growth factor-1 levels showed distinct growth advantages for San Juan Islands fish which were strongly associated with the early adoption of piscivory. However, consumption of larger crustaceans such as mysids and euphausiids was also associated with greater relative growth regardless of where individuals were captured. These findings highlight how spatiotemporal differences in prey quantity, prey profitability, and individual foraging strategies result in variable growth rates among salmon populations. Specifically, they emphasize the role of piscivory in promoting early marine growth for out-migrating Chinook salmon.

KEY WORDS: Somatic growth · Stomach content analysis · Scale morphometry · Insulin-like growth factor-1 · Oncorhynchus tshawytscha · Puget Sound

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Cite this article as: Davis MJ, Chamberlin JW, Gardner JR, Connelly KA, Gamble MM, Beckman BR, Beauchamp DA (2020) Variable prey consumption leads to distinct regional differences in Chinook salmon growth during the early marine critical period. Mar Ecol Prog Ser 640:147-169.

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