Effects of Flow and Food on Winter Movements of Juvenile Coho Salmon

We investigated how water flow, food availability, and individual fish size or condition affected the downstream movement of juvenile coho salmon Oncorhynchus kisutch exposed to winter conditions in artificial channels. The experimental design involved four treatments (two flow treatments crossed with two feeding treatments). Our results indicated that a water flow increase with winter conditions caused coho salmon to emigrate from our experimental channels, and the magnitude of emigration was higher when the flow increase was higher. Fish emigration rate decreased as temperature fell, but it was not affected by the presence of food, even though the fish continued to feed at temperatures below 4°C.