Dworshak Dam Impacts Assessment and Fisheries Investigations Project, 1993 Annual Report

Download or read book Dworshak Dam Impacts Assessment and Fisheries Investigations Project, 1993 Annual Report written by and published by . This book was released on 1995 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: We monitored the kokanee Oncorhynchus nerka kennerlyi population in Dworshak Reservoir, Idaho, by mid-water trawling and counting spawners in representative streams. Our estimates of age 1 kokanee abundance in 1993 were the highest on record; 556,000 fish. These fish resulted from last years record year class of age 0 kokanee. Age 2 kokanee were also abundant, achieving their second highest level on record. Dworshak Dam discharged less water between July 1, 1992 and June 30, 1993 than any of our recent years of study (the lowest since 1986-1987). Based on a past relationship with an r2=0.62, we expected age 2 kokanee abundance to be very high with this low level of discharge. We estimated mature kokanee abundance by trawling, which correlated well (r2=.89) to standardized spawner counts. This gives us the means to convert the older spawner count data into age 2 kokanee estimates. It is also a validation of spawner counts in tributary streams as an accurate method to obtain an index of adult kokanee abundance.