Emergence Timing and Life History in Chinook Salmon

Photoperiod at emergence and ration after ponding were varied in Yakima River spring Chinook salmon to test the hypothesis that seasonal timing of emergence and growth during early stages of development alter seasonal timing of smolting (under-yearling or yearling) and age of male maturation (age 1 or age 2).  Fish reared under conditions to advance fry emergence and accelerate growth had the greatest variation in the seasonal timing of smolting and the highest rates of early male maturation with most males maturing at age 1 (35-40%).  In contrast, fish with delayed emergence and slow growth had the least variation in phenotypes with most fish smolting as yearlings in the spring and no age-1 male maturation.  Growth (not emergence timing) altered rates of age-2 male maturation.  Results of this study demonstrate that altering egg and alevin development, as easily may occur through temperature shifts that accompany global climate change, can profoundly affect later life history transitions and the range of phenotypes within a spring Chinook salmon population.