Biotic and Abiotic Influences on Abundance and Distribution of Nonnative Chinook Salmon and Native ESA-Listed Steelhead in the Wind River, Washington

Abstract

Abstract Biotic and abiotic factors influence fish populations and distributions. Concerns have been raised about the influence of hatchery fish on wild populations. Carson National Fish Hatchery produces spring Chinook salmon Oncorhynchus tshawytscha in the Wind River, Washington, and some spawn in the river. Managers were concerned that Chinook salmon could negatively affect wild steelhead O. mykiss and that a self-sustaining population of Chinook salmon may develop. Our objectives were to assess: 1) the distribution and populations of juvenile spring Chinook salmon and juvenile steelhead in the upper Wind River; 2) the influence of stream flow and of each population on the other; and 3) if Chinook salmon populations were self-sustaining. We snorkeled to determine distribution and abundance. Flow in the fall influenced upstream distribution and abundance of juvenile Chinook salmon. Juvenile Chinook salmon densities were consistently low (range 0.0 to 5.7 fish 100 m-2) and not influenced by number of spa...