Identification and Enumeration of Steelhead Kelts at a Snake River Hydroelectric Dam

Autor: Martin S. Fitzpatrick, Ken Collis, Allen F. Evans, Roy E. Beaty
Rok vydání: 2004
Předmět:
Zdroj: Transactions of the American Fisheries Society. 133:1089-1099
ISSN: 1548-8659
0002-8487
DOI: 10.1577/t03-121.1
Popis: Improvement of iteroparity rates in U.S. Endangered Species Act (ESA)-listed Snake River populations of steelhead Oncorhynchus mykiss requires a means of distinguishing prespawn (mature) steelhead from postspawners (kelts) and sufficient kelt abundance to aid recovery efforts. We used ultrasound imaging of gonads to identify and enumerate prespawn steelhead and kelts incidentally collected in the juvenile bypass facility at Lower Granite Dam (LGR) on the Snake River, Washington. We also evaluated the accuracy of visual identifications based on external coloration and condition in relation to the known maturational status determined by ultrasound examinations. Steelhead (n = 1,353) were sampled during 10 weeks between April and June 2000, a period that spanned the peak of adult steelhead occurrence in the juvenile bypass system. Based on ultrasound appraisals, we estimated that kelts composed 94.6% of the 3,968 adult steelhead encountered in the LGR juvenile bypass system during the study period. ...
Databáze: OpenAIRE
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