Feasibility of using sonar to estimate adult coho salmon returns to the Kenai River

Description

A lack of quantifiable information concerning the magnitude of coho salmon Oncorhynchus kisutch returns to the Kenai River precludes defining exploitation rates or other key management objectives for this species. To determine the feasibility of estimating coho salmon abundance in the Kenai River using sonar, we evaluated a potential sonar site at river mile (rm) 14. Hydroacoustic sampling was conducted to measure background noise levels and radio telemetry was used to estimate the lateral distributions of adult salmon migrating past the site. We concluded that the distributions of migrating adult sockeye O. nerka and coho salmon overlapped significantly at rm 14. Background noise levels varied throughout the horizontal range that we measured and averaged -46.4 dB. The number of boats passing the site ranged from 0 up to 33 per hour, potentially compromising the amount of hydroacoustic sampling time available during some periods. These findings suggest that distinguishing between sockeye and coho salmon migrating concurrently in the Kenai River may not be practical, at this time, using differences in spatial distributions or modal target strength distributions.

Subjects

Genres

• Statistics

Series Statement

• Fishery data series -- no. 94-50.

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