Biological characteristics and population status of steelhead (Oncorhynchus mykiss) in southeast Alaska.

Abstract

We reviewed existing data to determine the range and distribution of steelhead (Oncorhynchus mykiss) in southeast Alaska, summarized biological characteristics, and determined population status of steelhead stocks. Unique or sensitive stocks that may require consideration in planning land management activities are identified within the data reviewed. Data sources were personal communications, reports, and unpublished data files of State and Federal agencies. Only eight winter-run stocks in southeast Alaska and two summer-run stocks in southwest Alaska had sufficient data to evaluate biological characteristics. Age structure, sex ratio, incidence and frequency of repeat spawning, and body length were similar among winter-run stocks, and consistent with coastwide trends of increasing freshwater age and body size of steelhead stocks in the northern portion of their range. Winter-run stocks appeared to have a greater proportion of repeat spawners (kelts) than summer-run stocks, and juvenile steelhead in the summer-run stocks generally spent 1 year less in both fresh water and the ocean. Assessment of escapement trends, run timing, and stock status is hindered by lack of adequate data both in number of stocks with sufficient data and the number of years of data available. Incomplete weir counts during immigration and emigration of adult fish and low sample sizes of escapement indices, both within and among years, decrease the reliability of estimates. Although stocks with sufficient data are not at risk, small run sizes that are typical of most steelhead stocks may be more susceptible to poor land management practices and overharvest than larger stocks.

Citation

Lohr, Samuel C.; Bryant, Mason D. 1999. Biological characteristics and population status of steelhead (Oncorhynchus mykiss) in southeast Alaska. Gen. Tech. Rep. PNW-GTR-407. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 29 p