Identification of spawning areas and the influence of environmental variation on freshwater migration timing and in-river movements of adult coho salmon in the Buskin River, Alaska

• Main Author: Stratton, Michelle Eileen
• Other Authors: Westley, Peter, Finkle, Heather, Falke, Jeff
• Format: Thesis
• Language: English
• Published: 2019
• Subjects: coho salmon; spawning; Alaska; Kodiak Island; migration; Fairbanks; Lake May; Kodiak
• Online Access: http://hdl.handle.net/11122/10645

Thesis (M.S.) University of Alaska Fairbanks, 2019 The timing of freshwater entry by anadromous salmonids varies markedly among species and populations within species and is frequently used as an indicator of local adaptation to sitespecific patterns of selection. Although complex stock structure is most often associated with large watersheds that have extensive habitat diversity, even small drainages can produce multiple co-occurring stocks that differ in migratory timing. In addition, migration timing can be influenced by within-year environmental conditions experienced by migrating individuals en route to spawning sites, staging near the river mouth in the ocean, or within the river itself. Each stage of migration through both freshwater and saltwater could be altered based on climatic drivers and how each individual fish reacts to these stressors. The objective of this thesis was to assess the potential for stock structure in Coho Salmon within a small coastal watershed on Kodiak Island, Alaska by 1) identifying important differences in spawning and holding locations associated with run timing, length, and stream life between main stem and tributary spawners, 2) quantifying the influence of large-, intermediate-, and local-scale climate variables on freshwater entrance timing and in-river movements. To address the first objective, fish were tracked to their spawning locations using acoustic telemetry in three spawning seasons (2015-2017). I detected no statistically or biologically meaningful differences in body size (length, mm) or migration timing into the river between main stem and tributary spawning fish. Unexpectedly, I found that a large portion of fish (80%) utilize the lake during their in-river migration suggesting the lake may represent critical staging habitat for adult Coho Salmon prior to spawning. I also identified holding habitat throughout the river that both spawning groups consistently used across years that also appears to be important to premature migrating Coho Salmon. In Chapter Two, ...