The Impact of Different Hatchery Rearing Environments on Smolt‐to‐Adult Survival of Spring Chinook Salmon

Abstract

AbstractThe aim of this study was to assess the effect of differing hatchery rearing environments on smolting, early male maturation, and smolt‐to‐adult return rates (SARs) in Chinook Salmon Oncorhynchus tshawytscha. In this investigation, SARs were compared for spring Chinook Salmon from Hood River stock reared at three different hatcheries and then released into the Hood River, replicated over three separate years (2010–2012). Differences in SARs were found both between rearing groups and release years. Smolts reared at Pelton Ladder had consistently higher SARs than those reared at either Parkdale or Carson hatcheries. Smolt length at release was positively correlated to SARs across years and rearing groups. In addition, multiple regression models suggested that attributes related to smolt quality were positively related to SARs while the minijack rate was negatively related to SAR. Migration of smolts downstream after release was also assessed. Larger smolts were faster downstream migrants and migration rate was positively related to subsequent SAR. Differences in smolt quality and SAR between rearing groups is attributed to differing patterns of growth in the different hatchery environments. The best‐performing smolts came from rearing groups that experienced a strong seasonal change in growth rate: relatively high growth in the summer, reduced growth and depletion of energetic stores in the autumn and winter, and then increased growth again in the spring. This pattern of seasonal anabolic and catabolic changes has been termed the wild fish template, and generating this physiological pattern generally may be applicable to hatchery‐reared Chinook Salmon.Received August 3, 2016; accepted December 20, 2016 Published online March 30, 2017