Size-at-Maturity Patterns Among Coastal Stocks of Chinook and Chum Salmon from the Oregon Coast: Testing Hypotheses for Harvest Pressure Vs. Oceanographic Conditions

Body size in salmon is an important factor in determining abilities for negotiating obstacles en route to spawning grounds, in fecundity, and in competing for successful mating opportunities.  Harvest in fisheries has been shown to select for smaller size-at-maturity in fishes.  In addition, certain oceanographic conditions are not conducive to growth, resulting in smaller size-at-maturity in fishes.  Here, we compare size-at-maturity trends from spawned-out Chinook and Chum salmon on their spawning grounds to address the questions of whether 1) upward or downward trends in size-at-maturity exist for Chinook and Chum salmon over time and space; 2) whether these trends correlate with different harvest scenarios or oceanographic regime shifts.  Finally, we compare the evidence between Chinook Salmon, a commercially and recreationally harvested fish, with those of Chum Salmon, a fish that is not directly harvested in Oregon, to address two questions:  1) Do size-at-maturity trends for Chinook Salmon correlate more strongly with harvest pressure or oceanographic regimes shifts? And 2) Do size-at-maturity trends for Chum Salmon correlate with oceanographic conditions?