In the previous paper, the author reported on a method to measure towing power of fish. It was found that a fish on which towing power measurement is being performed must overcome drag force as well as towing load.
In the present paper, methods for drag measurement were explained and the drag power was calculated. Then, towing power and drag power of a fish were combined together in a diagram. The diagram will be available not only for the estimation of maximum free swimming speed of fishes, but also for the revaluation of validity of the drag measurements.
Through the measurement at relatively rapid stream in running water, live fishes showed rather higher drag than freshly killed fishes.
These drag increments were considered effect of mouth opening action and operation of fins to keep body stability. Moreover, in even a fins-amputed fish, it was observed that postures of twisting or bending body caused a higher drag.
