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Over-winter Survival and Habitat Use by Juvenile Coho Salmon (Oncorhynchus kisutch) i
By John E. Ford, David G. Lonzarich
Journal of Great Lakes Research, Volume 26, Issue 1, 2000, Pages 94-101, ISSN 0380-1330, DOI: 10.1016/S0380-1330(00)70676-9.
Dramatic declines in commercial and recreational fisheries for coho salmon (Oncorhynchus kisutch) in Lake Superior have raised questions about the natural factors that limit their productivity. Snorkeling surveys were conducted during the winters of 1995-96 and 1996-97 to estimate over-winter mortality and determine winter habitat use by juvenile coho salmon in two spring-fed tributaries of Chequamagon Bay, Lake Superior. Results indicated high densities of juvenile coho salmon in pool habitats of the two streams ( = 0.85 fish/m2) and high over-winter survival (> 45%). Regression analyses revealed no significant relationships between fish distribution and physical habitat variables (large woody debris, overhead cover, and pool size). No shift in habitat use over the winter was found. These results contrast sharply with findings from the Pacific Northwest where juvenile coho salmon generally occupy complex pool habitats during the winter. Although streams of the Great Lakes region are similar in many respects to Pacific streams, differences, particularly in stream flow regimes, indicate that the early life history of coho salmon populations in these two regions differ dramatically. These observations may have important implications on the management of stream habitats in the Great Lakes.
Keywords: Coho salmon; Oncorhynchus kisutch; winter ecology; juvenile survival; Lake Superior