Predation on Naturally-Produced Chinook Salmon Parr in the Lower Salmon River, New York

Since being introduced into Lake Ontario in the late 1960s, Chinook salmon (Oncorhynchus tshawytscha) have been successfully reproducing in the wild. Recent research indicates that approximately 62% of returning adults are of wild origin. The Salmon River contributes the largest number of naturally-produced Chinook salmon of any Great Lakes tributary, though hatchery-reared juveniles are used to bolster stocks. Because of the importance of this species to the local fishery and the significant contribution of naturally-produced individuals, it is important to understand the factors affecting their recruitment dynamics. Various fish communities can be found throughout the Salmon River and its tributaries, presenting Chinook parr with significant predation pressures. The lower Salmon River presents a unique suite of predators, many of which are typical of lentic systems. These predators were sampled near the mouth of the river by boat electrofishing between May and July 2010 to determine the importance of Chinook salmon parr in their diets. Gastric evacuation and dissection were used to quantify stomach contents by type and percent composition. These results were analyzed as a function of predator species, size, water temperature, flow, and time. Preliminary results indicate that Chinook salmon parr are commonly utilized as prey by rock bass and yellow perch in the lower Salmon River. Inter-annual variations in parr density may result in considerable food web fluctuations, including altered pressures on resident fish prey. Additionally, this work will allow a more complete picture of the predation pressures facing naturally-reproduced salmon, giving researchers a better understanding of the factors that contribute to Chinook salmon recruitment.