An exploration of hatchery and wild chum salmon returns in Southeast Alaska

• Main Author: Stansberry, Kelsey L
• Format: Text
• Language: unknown
• Published: ScholarWorks at University of Montana 2023
• Subjects: Pink salmon; Alaska
• Online Access: https://scholarworks.umt.edu/umcur/2023/oral_presentations/17; https://scholarworks.umt.edu/context/umcur/article/2587/type/native/viewcontent/Stansberry_UMCUR_Presentation.pptx

Salmon enhancement programs are a common restoration practice to maintaining a sustainable commercial fishery, but there is concern on how hatchery straying impacts the overall fitness of wild salmon stocks. Several organizations in Prince William Sound and SE Alaska developed a partnership to cohesively research and analyze the impacts of hatchery chum and pink salmon stray rates on wild populations. The goals of this partnership are to (1) understand the regional genetic stock structure of pink and chum salmon, (2) examine the extent and annual variability in straying of hatchery pink salmon in Prince William Sound and chum salmon in PWS and Southeast Alaska, and (3) evaluate impacts on productivity of wild stocks due to straying of hatchery fish. Hatchery fish have thermal markings on their otoliths (ear bones) unique to the hatchery and brood stock. In the summer of 2022, I collected otoliths, tissue, and scale samples from chum carcasses to identify hatchery and wild fish. For my analyses, I accessed data from the last decade on three focal streams near hatcheries to better understand the potential impact of straying from hatcheries on these stream populations. The proportion of hatchery fish in these spawning populations ranges from 29% - 57%, averaged over decade for each stream. I investigated three questions: (1) Which hatchery are they straying from, does distance explain variation in hatchery origin? (2) How does the hatchery proportion of the population change through time and is that change synchronous across streams? (3) Are there differences in age of maturation? Because hatchery fish have faster early growth rates, they might be returning at a younger age than wild fish. What is the age structure of return adults and are they potentially younger than wild fish for the region? This analysis can add to the greater Alaska Hatchery Research Project which will guide future decisions and advance the understanding of the ecological and evolutionary dynamics of wild and hatchery interactions.