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Division: Sport Fish
Title: Stock assessment of coho salmon from the Kenai River, Alaska, 1999
Author: Massengill, R. L
Year: 2007
Report ID: Alaska Department of Fish and Game, Fishery Data Series No. 07–69, Anchorage
Abstract: In spring 1998, 101,728 wild coho salmon Oncorhynchus kisutch smolt were captured in the Kenai River drainage, marked with an adipose finclip and injected with a coded wire tag (CWT), and released. Marked adults were recovered from selected commercial fisheries of Upper Cook Inlet (UCI), Alaska. In summer 1999, 125,343 coho salmon were harvested among all UCI commercial fisheries, 22,605 were examined from the Northern District fishery (72% of the harvest from this area), 33,158 were examined from Central District drift gillnet fishery (51% of the harvest in this area), and 4,149 were examined from the Central District eastside set gillnet fishery (36% of the harvest in this area). A total of 1,567 adipose–clipped fish were observed in the unmixed fishery samples, of which 1,539 were recovered, 1,433 bore a decodable CWT, and 185 were identified as being of Kenai River origin. In the Kenai River in fall 1999, using fish wheels and drift gillnets, a total of 2,476 coho salmon were captured and examined, 313 were missing the adipose fin, and 299 bore a Kenai River CWT. Significant temporal variation in the tag–bearing proportion measured at all inriver sampling locations precluded an accurate estimate of the tag–bearing proportion passing through marine commercial fisheries and accurate estimates of commercial harvest of Kenai River–bound coho salmon. However, a point estimate of the overall tagged proportion of the return ( =0.121, SE = 0.007) was generated from a subset of inriver data, as were estimates of the potential minimum ( =0.097, SE = 0.007) and maximum return ( =0.179, SE = 0.014). Three resulting harvest estimates were compared to evaluate the 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 should be qualified. An estimated 2,928 (SE = 297) coho salmon of Kenai River origin were harvested by the Central District eastside set gillnet fishery, 820 (SE = 134) by the Central District drift gillnet fishery, and 171 (SE = 49) by all Northern District set gillnet fisheries for a total of 3,919 (SE = 330). Kenai River origin coho salmon represented 25% of the total eastside set gillnet harvest of coho salmon, 1.3% of the drift gillnet harvest, and 0.5% of the Northern District set gillnet harvest. Based on the number of live smolt released with an adipose clip at the Moose River in 1998 and the number of adult coho salmon examined for adipose fin status in the Kenai River fish wheel samples in 1999, an estimated 797,798 (SE = 41,940) smolt emigrated from the Kenai River in 1998.
Keywords: coho salmon, Oncorhynchus kisutch, population assessment, sustained yield, contribution, commercial harvest, coded wire tag, Kenai River, smolt abundance, wild, fresh water, marine.