Cattle and Salmon II: Interactions Between Cattle and Spawning Spring Chinook Salmon (Oncorhynchus tshawytscha) in a Northeastern Oregon Riparian Ecosystem

Abstract

The study addressed the interaction between cattle and spawning spring chinook salmon late in the summer, when it is common for cattle to be present in pastures that have streams where spawning occurs. We addressed the occurrence of spawning in the study area and 2 potential impacts of cattle behavior during chinook salmon spawning: 1) disruption of spawning behavior by the presence of cattle near the redd and 2) the frequency of actual cattle contact with redds. Frequency of salmon redds was not significantly different in the stream reaches accessible to cattle compared with excluded reaches. Salmon continued preexisting patterns of behavior while cattle were within visible range of a redd. Cattle were seldom close to a redd and the chance for direct interaction to occur was minimal. When cattle were visibly near the active redd, cattle remained greater than 3.0 m from the active redd 84% of the time. Of the total time redds were observed, cattle contacted the redds <0.01% of the time. Previous studies have shown salmon that are harassed during spawning can retain eggs and even go completely unspawned. All salmon fully spawned in the study area in both years of the study.