A New Apparatus for Measuring Maximum Swimming Speeds of Small Fish

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Abstract
An apparatus and method were developed to obtain comparative measurements of maximum swimming speeds of small fish. The present method is considered useful in bioassays for measuring sublethal effects of pollutants. The fish swim in an open-topped oval channel with a circumference of 1.48 m. A variable speed 1/8-hp motor turns 2 paddle wheels and creates measured currents up to 30 m per minute. Fish are not required to swim at the same velocity as the water in the chamber. Rather, they swim in a current which is greater than their maximum swimming speed and which moves them backwards in the channel. The average maximum swimming speed for a group of 4 to 6 fish is calculated from the current velocity, circumference of the channel, and the number of laps lost during a specific time period. Tests with fathead minnows, Pimephales promelas, showed that different current velocities gave the same swimming speed as long as the current was greater than the swimming speed of the fish. A swimming period of 3 min. gave consistent results. Large mouth bass fingerlings, Micropterus salmoides, which were conditioned by exposing them once daily to the standard test in the chamber, showed a marked increase in swimming ability after 3 days. Fed and unfed fish showed equal increases in performance and the conditioned fish developed a slightly higher active metabolism.

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