EFFECT OF PRE-RELEASE GROWTH TRAJECTORIES ON ADULT MATURATION PATTERNS IN COLUMBIA RIVER SPRING CHINOOK SALMON

Brian Beckman*, Dina Spangenberg, Ryan Gerstenberger, Deb Harstad, Chris Brun, Shelly Nance, Don Larsen
 
Northwest Fisheries Science Center,
National Marine Fisheries Service,
Seattle Wa,
brian.beckman@noaa.gov

Over 100,000,000 juvenile Chinook salmon are released annually from hatcheries into the Columbia River (Oregon, Washington and Idaho).  Goals for returning adults are 1) provide harvest opportunities and 2) spawn naturally in rivers to supplement juvenile production for depleted populations of conservation concern.  Thus, some hatcheries are tasked to produce juvenile salmon that not only survive and return as adults, but also mature at sizes and ages similar to that found in natural populations.

Dogma suggests that age and size of returning adults is a population characteristic with a genetic basis.  However, it has become apparent that the proportion of adult male fish returning as jacks (age 3, 1 year in advance of the modal age of Columbia River Chinook salmon populations) is greater in hatchery populations than naturally rearing populations of the same stock.  This difference in the proportion of adults maturing at a given age could be caused by a) domestication selection or b) environmental differences during early rearing that affect age at maturation.  In this talk we will present data demonstrating that differing growth trajectories during juvenile hatchery rearing are related to different adult demographics.  Based on these data, we developed some general guidelines for hatchery rearing that may improve our ability to match adult maturation patterns of hatchery and wild Chinook salmon.