Effects of Stream Cleaning on Juvenile Coho Salmon and Dolly Varden in Southeast Alaska

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Abstract
This paper describes the effects of selective removal of woody debris on populations of juvenile coho salmon Oncorhynchus kisutch and Dolly Varden Salvelinus malma in two small streams on Prince of Wales Island, Alaska, during the summers of 1979–1981. These streams contained debris left when surrounding forests were clear‐cut in the late 1960s. Debris smaller than 60 mm in diameter and larger debris not embedded in the stream channel were manually removed from half of the study reach on each stream in 1979 by state‐of‐the‐art techniques. Immigration and emigration of fish from the study sections and intrastream movements were very limited after an initial period of population adjustment in the spring regardless of treatment. Population densities and production of both species were typically higher in sections where debris accumulations had not been removed. Production of age‐0 + and age‐1 + coho salmon and age‐1 + and age‐2 + Dolly Varden during the June‐September period ranged from 0.70 to 2.22 g/m2 in the cleaned sections and from 0.84 to 2.10 g/m2 in the uncleaned sections. Carrying capacities for both species were lower in cleaned sections despite the use of selective techniques for removing woody debris.