Variations in Size, Growth and Survival of Hatchery and Wild Columbia River Chinook Salmon in the Northern California Current

There is increasingly clear evidence that variable ocean conditions are directly responsible for large-scale variation in the return of adult Chinook salmon to the Columbia River.  There is also accumulating evidence that variable marine mortality occurs soon after smolts enter the ocean.  Finally, inter-annual variation in growth of smolts in the ocean is correlated with adult returns. However, it I not yet clear if and/or how differences in size and growth among smolts in the ocean may subsequently affect differential survival.  In this talk we will present data showing differences in size and growth among yearling hatchery Chinook salmon smolts sampled off the Oregon/Washington Coast.  We will also present data suggesting that relations between size and growth vary with ocean conditions.  Together, these suggest that growth may be food limited in the ocean in some years and that smolts may vary in their ability to exploit food resources across years.  Finally, we will compare stock-specific size and growth rate of clipped (hatchery) and un-clipped (wild?) smolts captured at the same time and place in the ocean.  The implications of these findings for hatchery rearing strategies and hatchery vs wild interactions in the ocean will be discussed.