David Beauchamp, University of Washington, on “Pelagic Food Web Ecology in Puget Sound: Implications for Marine Growth & Survival of Chinook Salmon”:
We need to consider the next life stage for chinook and the processes involved.
Smolt to adult survival is highly correlated with body weight in July, suggesting this weight represents ‘critical size’. Offshore growth in May to July is a ‘critical period’ for determining survival.
Possible factors affecting growth and survival: feeding rate; food availability (data limitations); temperature; competition (within species, among salmon, forage fish); predation
Total ocean survival is tightly linked to early offshore marine growth. Offshore feeding was significantly higher during years of high survival.
Chinook must feed at a high rate (>60% max) to grow and minimize size-selective mortality.
Conclusions: Feeding rate is more important than temperature. Temperature effects are minimal, but non-linear. Variable feeding rate suggests food limitation, data on needed on their prey. Competition by herring more important than competition between hatchery and wild chinook and other salmon.