PARENT SESSION
Poster Session #23: Fish, Lakes, Streams, and Wetlands.
Wednesday, August 8, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Distribution and behavior of coho salmon during summer rearing period in a Lake Superior tributary.

Franckowiak, Ryan¹, Allen, Matthew¹, Lonzarich, David ¹, ¹

ABSTRACT- In their native range of western North America, coho salmon (Oncorhynchus kisutch) are exposed to a variety of population controls during their freshwater residency. The first summer is particularly stressful, as low stream flows create conditions that intensify biotic interactions, limit distribution and select for aggressive and sedentary behaviors. Testing the premise that flow conditions can shape the ecology of juvenile salmon, we examined how periodic summer flooding in a tributary stream of Lake Superior, Wisconsin affected the distribution, movement and social structure of a population established in the drainage in the 1970s. Snorkeling approximately 2 kilometers of the stream at ten-day intervals in summer 2000, we found that salmon occupied a wide range of habitats; that they moved a great deal; and that they were as likely to occur in aggregations as they were in social hierarchies. We suspect that the variable summer flows in this stream may alter the nature of intraspecific interactions by limiting the ability of salmon to establish social hierarchies. These results raise the possibility that coho salmon might be adapting to the environmental challenges of streams in this region.

KEY WORDS: stream, fish, ecology, coho salmon