Abstract
The resistivity fish counter is widely used in Europe to count Atlantic salmon that pass through in-river structures (e. g., a Crump weir). The use of the counter is known to be an accurate and economical way of counting fish. However, the counter is rarely used in Japan. This study aims to establish a method for counting fish that pass through a fish way in Japan by using the resistivity fish counter.
A platform equipped with the sensor component of the resistivity counter was assembled in the fishway at the headwork of the Tone-ozeki. We designed the platform in accordance with the requirements of a fish way for Atlantic salmon (i. e., with appropriate velocity and height of water flow). We counted the number of salmon passing through the fish way during the spawning season by using the resistivity fish counter on the platform.
The sensor component of the fish counter was captured by a video camera from directly above, for a total of 19 h. The number of fish was counted from the video analysis. The accuracy of the number of salmon determined by using the fish counter was evaluated by comparing the result obtained from the fish counter with that obtained from the video analysis.
The accuracy of the number of salmon counted by using the fish counter was found to be 96%. The factors that might decrease the accuracy of the counter, the method of designing the platform in accordance with the requirements of a fish way, and cost for this study were considered. Methods for improving the accuracy of the counter are discussed.
