Distribution and Habitats of Juvenile Coho Salmon in Tributaries of the Little Susitna River, Alaska

The upper Little Susitna drainage is a relatively intact system and provides habitat for multiple Pacific salmon runs. However, because this area is currently seeing increased development and urbanization and increased fishing pressure, there is concern regarding the conservation status of Little Susitna salmon stocks. Data on these stocks are limited; we lack a full understanding of juvenile rearing habitat, and what habitat factors limit the distribution and production of Pacific salmon in the region. For example, the rearing habitat for juvenile coho (Oncorhynchus kisutch) is poorly understood, specifically in areas located within the headwaters of drainages. These areas include aquatic ecosystems between 150 and 450 m in elevation with high gradient and fast moving water. I plan to use a habitat modeling approach to determine the range of habitats used by juvenile coho including habitats that are most limiting or productive for a species at selected spatial scales. During the summer of 2010, I sampled select headwater tributaries of the Little Susitna drainage using a continuous sampling technique to investigate spatial patterns in fish distribution, in conjunction with a streamwide assessment of habitat. I used backpack electrofishers to sample fish distributions throughout stream reaches delineated at 200 m. Habitat variables I recorded included temperature, pool frequency, wood debris, gradient, elevation, substrate, and distance from mainstem habitat. During 2010, habitat characteristics were measured on 59 stream reaches and 52 reaches were sampled for fish. Within these 52 reaches, I aged 463 fish using scales, and 352 fish using otoliths. These data will allow me to model habitat use and identify areas of the Little Susitna region that are important for juvenile coho salmon. This will allow for more strategic and informed management of these populations with implications towards conservation and restoration practices occurring in the Matanuska-Susitna regions. Furthermore, this work will help generate hypotheses regarding mechanisms that regulate the distribution and productivity of juvenile coho salmon in the region.