Effects of Logging on the Abundance and Seasonal Distribution of Juvenile Steelhead in Some Southeastern Alaska Streams

Abstract

Eighteen streams in six locations in southeastern Alaska were examined for the effects of logging on juvenile steelhead (Salmo gairdneri) populations. Three types of streams were examined at each location: a stream in undisturbed old-growth forest; a stream in a clear-cut area with strips of forest (buffer strips) along the stream bank; and a stream in a clear-cut area logged on at least one bank. Within each stream type, three reaches were sampled. Few juvenile steelhead were found in reaches where juvenile cutthroat trout (Salmo clarki) were present, and no juvenile steelhead were found in streams with a low-flow discharge (<0.06 m 3/s). Only two study sites, Prince of Wales Island and Mitkof Island, had juvenile steelhead in all three stream types. Fry (age 0) and parr (age I and older) were sampled in summer and winter at the Prince of Wales Island site; parr were sampled in summer at the Mitkof Island site. Logging appeared to affect the growth of steelhead fry and the abundance and distribution of both fry and parr. On Prince of Wales Island, fry were more abundant and larger in the clear-cut reaches than in the old-growth or buffered reaches. Parr density in summer was highest in the clear-cut reaches at both sites but, by winter, had decreased 91% in the clear-cut reaches and had increased 100 and 400%, respectively, in the old-growth and buffered reaches. Parr were migrating during fall and winter; therefore, the effects of logging on their growth could not be assessed.