Postsmolt Growth More Important than Initial Growth at Sea

Photo credit: USGS

Photo credit: USGS

WINNER: 2014 Best Paper, Marine and Coastal Fisheries

Over the last 20-30 years, the abundance of steelhead Oncorhynchus mykiss in the Keogh River, British Columbia, has declined substantially. Increased marine mortality has been cited as the main reason for this decline, with size at ocean entry appearing to be the main factor determining recruitment. However, in a new study in Marine and Coastal Fisheries, Kevin D. Friedland of the National Marine Fisheries Service and his colleagues found other factors to be affecting marine survival. Through restrospective growth analysis using scales from returning steelhead, they found that the growth shortly after smolt transition was a strong predictor of survival to adulthood in the Keogh River from 1977 to 1999. Further stating that this growth may alleviate any initial size differences in smolts, lessening the effect of size of ocean entry. They also found that this growth was closely related to sea surface temperatures during the June-December period following ocean entry. This article is important because it reconfirms that the survival pattern of the Keogh River steelhead population has changed, with sustained growth conditions during summer and fall of the postsmolt year being more important than initial growth at sea.


Friedland, K. D., B. R. Ward, D. W. Welch, and S. A. Hayes. 2014. Postsmolt growth and thermal regime define the marine survival of steelhead from the Keogh River, British Columbia. Marine and Coastal Fisheries 6:1-11.

Members click below for the January 2016 Fisheries magazine’s complete issue. Non-members, join here.

This content is for members only. Please login.