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Aquat. Living Resour. 11 (1998) 61-74
DOI: 10.1016/S0990-7440(98)80062-4
Fixed-location riverine hydroacoustics as a method of enumerating migrating adult Pacific salmon: comparison of split-beam acoustics vs. visual counting
Hermann J. Enzenhofer1, Norm Olsen2 and Timothy J. Mulligan21 Fisheries and Oceans Canada, Science Branch, Pacific Region Cultus Lake Salmon Research Laboratory, 4222 Columbia Valley Highway Cultus Lake British Columbia V2R 5B6 Canada
2 Fisheries and Oceans Canada, Science Branch, Pacific Region Pacific Biological Station, Nanaimo British Columbia V9R 5K6 Canada
(Received 20 August 1997; accepted 13 January 1998. Available online 11 November 1999.)
Abstract
A split-beam hydroacoustic system with automatic tracking of individual fish is being used to estimate the number of upstream
migrating adult Pacific salmon in the Fraser River in British Columbia, Canada. To determine the bias and variance of the
estimates of migrating fish numbers produced by this system, we compare simultaneous acoustic and visual estimates. These
data demonstrate that, as fish densities increased, both a 4° × 10° and an 8° transducer produced lower estimates than the
visual count. However, in the region of fish densities typically observed for migrating salmon, the 4° × 10° transducer estimates
did not differ significantly from the visual count. A detailed description of the experimental configuration is given, including
how the acoustic and video data were synchronized. Analyses of the data indicate that the size and shape of the acoustic beam
has a pronounced effect on the bias of the acoustic estimates. In addition, the performance of the tracking software deteriorates
as fish densities become very high.
Key words: Anadromous species / stock assessment / split-beam sonar / Oncorhynchus nerka / Oncorhynchus gorbuscha / Canada (British Columbia)
© Elsevier, IRD, Inra, Ifremer, Cemagref, CNRS 1998