Abstract
We developed resistivity fish counter unit, which is a resistivity fish counter with rectangle frame type electrodes installed inside a polyvinyl chloride tube. In this study four resistivity fish counter units were assembled in the fish way at the Tone-ozeki weir at upstream period for small fish. We counted the number of small fish passing through each fish counter units. The each fish counter units was captured by a video camera from directly above, for 100 minutes. The number of fish was counted from the video analysis. The accuracy of the number of fish counted 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 passing fish counted by using the fish counter was about 90% when number of fish, which pass through a fish counter unit, was less than 50/min. However the accuracy of the number of fish was about 60% when number of fish was more than 50/min because a number of fish pass through a fish counter unit together. The correction method using a correction formula was proposed to improve the counting accuracy by the resistivity fish counter in case number of fish is more than 50/min. It was shown that number of fish per 10 minutes can be counted with an accuracy of nearly 100% using the correction method.
