Presentation Abstract

The growth and survival of juvenile Chinook salmon (Oncorhynchus tshawytscha) are determined in part by biotic and abiotic conditions experienced during their first marine summer. Of the biotic conditions, the quality of available prey is integral for optimal growth and survival. Current studies that investigate the effect of variable prey quality on salmon growth approximate energy density using literature values. This approach ignores fine-scale taxonomic as well as spatial and temporal differences in prey quality. To address these possible sources of error, monthly zooplankton tows were performed in Saanich Inlet, Cowichan Bay and Maple Bay off the coast of Vancouver Island, British Columbia in the summer of 2017. Individuals were separated to the species level and wet, dry and ash weights were measured for each zooplankter. Energy density was calculated from an established model, which relates the ash-free dry weight of individuals to energy density values. Early results suggest statistically significant differences in energy density between several species of hyperiid amphipods, which represent a large proportion of O. tshawytscha diet in some years. Other important species groups such as euphausiids, crab zoea and gammerid amphipods differed in energy density from previously reported studies in other locations suggesting spatial variability in energy density. These early results suggest that fine-scale taxonomic variability in energy density exists and that species-specific energy density may vary across space and time. Studies that draw conclusions from literature values of energy density without direct measurement should be cautious in extrapolating with these data in relation to their study system.

Session Title

The Salish Sea Marine Survival Project: Phytoplankton and Zooplankton

Keywords

Salmon, Prey, Energy density

Conference Track

SSE11: Species and Food Webs

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE11-270

Start Date

5-4-2018 4:45 PM

End Date

5-4-2018 5:00 PM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 5th, 4:45 PM Apr 5th, 5:00 PM

Fine-scale taxonomic and spatiotemporal variability in the energy density of prey for juvenile Chinook salmon (Oncorhynchus tshawytscha)

The growth and survival of juvenile Chinook salmon (Oncorhynchus tshawytscha) are determined in part by biotic and abiotic conditions experienced during their first marine summer. Of the biotic conditions, the quality of available prey is integral for optimal growth and survival. Current studies that investigate the effect of variable prey quality on salmon growth approximate energy density using literature values. This approach ignores fine-scale taxonomic as well as spatial and temporal differences in prey quality. To address these possible sources of error, monthly zooplankton tows were performed in Saanich Inlet, Cowichan Bay and Maple Bay off the coast of Vancouver Island, British Columbia in the summer of 2017. Individuals were separated to the species level and wet, dry and ash weights were measured for each zooplankter. Energy density was calculated from an established model, which relates the ash-free dry weight of individuals to energy density values. Early results suggest statistically significant differences in energy density between several species of hyperiid amphipods, which represent a large proportion of O. tshawytscha diet in some years. Other important species groups such as euphausiids, crab zoea and gammerid amphipods differed in energy density from previously reported studies in other locations suggesting spatial variability in energy density. These early results suggest that fine-scale taxonomic variability in energy density exists and that species-specific energy density may vary across space and time. Studies that draw conclusions from literature values of energy density without direct measurement should be cautious in extrapolating with these data in relation to their study system.