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 ([lesser than] 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 (2018 : Seattle, Wash.)
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
Genre/Form
presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Smolting; Sockeye salmon--Salish Sea (B.C. and Wash.)--Growth
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
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 ([lesser than] 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.
