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Division: Sport Fish
Title: Assessment of coho salmon from the Kenai River, Alaska, 2004.
Author: Massengill, R.
Year: 2007
Report ID: Alaska Department of Fish and Game, Fishery Data Series No. 07-79, Anchorage.
Abstract: Wild coho salmon Oncorhynchus kisutch smolt were captured in the Kenai River drainage in spring 2003, marked with an adipose finclip and injected with a coded wire tag (CWT). Marked adults were recovered in 2004 from selected commercial fisheries in Upper Cook Inlet (UCI), Alaska, and from the Kenai River drainage. Mark-recapture data were used to estimate the UCI commercial harvest of Kenai River coho salmon in 2004 and smolt abundance in 2003. There were 309,548 coho salmon harvested among all UCI commercial fisheries and 97,043 (31%) were examined for marks. There were 28,461 coho salmon (64% of the harvest) examined from Northern District harvests, 53,139 (27%) examined from Central District drift gillnet harvests, and 4,991 (17%) examined from Central District eastside set gillnet harvests. Among these, 1,055 adipose-clipped fish were observed: 1,044 were recovered, 941 bore a readable CWT, and 181 were identified as being of Kenai River origin. Significant temporal variation in the tag-bearing proportion of Kenai River coho salmon sampled inriver precluded an accurate estimate of the tag-bearing proportion passing through the commercial fisheries and those commercially harvested. However, an overall tagged proportion estimate ( ) of the return ( =0.100, SE=0.003); was generated from inriver sampling. Estimates were also generated for potential minimum ( =0.068, SE=0.005) and maximum ( =0.137, SE=0.009; =7.3, SE=0.486) tagged proportion. These harvest estimates were compared to evaluate the practical impact of the temporal variation on commercial harvest estimates. The evaluation indicated that harvest estimates based on the overall tagged proportion are practical for assessment and planning purposes, but must be qualified for addressing allocation issues. An estimated 5,921 (SE=1,092) Kenai River coho salmon were harvested by the Central District eastside set gillnet fishery, 4,251 (SE=531) by the Central District drift gillnet fishery, and 977 (SE=218) by all Northern District set gillnet fisheries for a total of 11,149 (SE=1,234). These estimates represented 19.7% of the total eastside set gillnet harvest of coho salmon, 2.1% of the drift gillnet harvest, and 2.2% of the Northern District set gillnet harvest. Based on the number of live smolt released with an adipose-clip at the Moose River in 2003 (120,305), and the proportion of adult coho salmon examined with an adipose-clip in Kenai River fish wheel samples in 2004, an estimated 1,196,310 (SE=37,100) smolt emigrated from the Kenai River in 2003.
Keywords: coho salmon, Oncorhynchus kisutch, population assessment, sustained yield, contribution, commercial harvest, coded wire tag, Kenai River, smolt abundance, wild.