Estimation of the abundance of late-run chinook salmon in the Kenai River based on exploitation rate and harvest, 1996

Description

The inriver return of the late run of chinook salmon to the Kenai River was estimated to assess the accuracy of the inriver return estimate obtained with split-beam hydroacoustic (sonar) gear. In this study inriver return was estimated as a function of harvest and exploitation rate by the sport fishery between the chinook salmon sonar site and the Soldotna Bridge from 1-31 July 1996. Harvest estimated by an onsite creel survey was 5,682 (SE = 358) fish. Exploitation rate was estimated by monitoring and determining fate of chinook salmon fitted with a radio transmitter. Marked chinook salmon were combined into eight groups based on time of entry into the river. Exploitation rate did not differ (P > 0.05) by sex, size, or time-of-entry group. A total of 47 marked chinook salmon were harvested by the sport fishery. The estimated exploitation rate was 0.144 (SE = 0.003). The estimated inriver return of 39,356 (SE = 3,535) fish was significantly (P = 0.005) less than that obtained by sonar (49,755 fish; SE = 1,037). The two estimates of inriver return were not different (P 0.18) during the period 1-13 July, when approximately 25,000 sockeye salmon entered the river, or 14-31 July, when over 600,000 sockeye salmon entered the river. However, the estimates differed by only 1% during the first period but by 13% during the second period. Differences between the estimates of the entire month and of 14-31 July indicate that the sonar gear may be classifying some targets as chinook salmon that are actually sockeye salmon. Sonar data other than that currently used to classify targets as chinook salmon should be examined to better discriminate and more accurately determine targets that are chinook salmon.

Subjects

Series Statement

• Fishery data series -- no. 98-6.

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