Event Title

Relationship between early marine growth and returning adults of Fraser sockeye salmon

Presentation Abstract

Smolt-to-adult survival of sockeye salmon returning to Chilko Lake was lower than average for the 77.1 million smolts that entered marine waters in 2007 (<0.25%), and high for the 71.9 million that entered the ocean in 2008 (6.7%). As recruitment dynamics of Pacific salmon is generally expected to be determined by growth during their early marine life, we tested the hypothesis that early marine growth of Chilko Lake sockeye salmon was higher in 2007 than in 2008. We used daily growth increment from otoliths to determine how the early marine growth rate of juvenile Chilko Lake sockeye salmon differed between years of low and high survival after 30-60 days at sea, the period hypothesized to be critical for survival. Juveniles that entered the ocean in 2008 grew at a significantly faster rate than those in 2007. The 2008 juveniles spent on average the same number of days at sea as the 2007 juveniles, but were significantly larger than those caught in 2007, despite the fact that they entered the ocean at a smaller size. Somatic growth rates of the smolts that entered the ocean in 2008 were on average 20% faster than the smolts that entered the ocean in 2007, suggesting that the higher survival observed in 2008 may be related to ocean conditions that were favorable to growth. To test this hypothesis further, we examined the relationship between adults return and early marine growth rate during the first 30-60 days at sea and other variables using 10 years of data (2004-2013). We found that somatic growth rate explained the greatest proportion of the variation in adult returns, after taking considering the number of out-migrating smolts.

Session Title

The Salish Sea Marine Survival Project: Juvenile Salmonid Growth and Survival

Conference Track

SSE11: Species and Food Webs

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE11-490

Start Date

5-4-2018 11:00 AM

End Date

5-4-2018 11:15 AM

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, 11:00 AM Apr 5th, 11:15 AM

Relationship between early marine growth and returning adults of Fraser sockeye salmon

Smolt-to-adult survival of sockeye salmon returning to Chilko Lake was lower than average for the 77.1 million smolts that entered marine waters in 2007 (<0.25%), and high for the 71.9 million that entered the ocean in 2008 (6.7%). As recruitment dynamics of Pacific salmon is generally expected to be determined by growth during their early marine life, we tested the hypothesis that early marine growth of Chilko Lake sockeye salmon was higher in 2007 than in 2008. We used daily growth increment from otoliths to determine how the early marine growth rate of juvenile Chilko Lake sockeye salmon differed between years of low and high survival after 30-60 days at sea, the period hypothesized to be critical for survival. Juveniles that entered the ocean in 2008 grew at a significantly faster rate than those in 2007. The 2008 juveniles spent on average the same number of days at sea as the 2007 juveniles, but were significantly larger than those caught in 2007, despite the fact that they entered the ocean at a smaller size. Somatic growth rates of the smolts that entered the ocean in 2008 were on average 20% faster than the smolts that entered the ocean in 2007, suggesting that the higher survival observed in 2008 may be related to ocean conditions that were favorable to growth. To test this hypothesis further, we examined the relationship between adults return and early marine growth rate during the first 30-60 days at sea and other variables using 10 years of data (2004-2013). We found that somatic growth rate explained the greatest proportion of the variation in adult returns, after taking considering the number of out-migrating smolts.