A Method for Determining Basal Metabolism of Fishes.

Abstract

Various methods used by other workers in metabolism experiments with fishes were considered inapplicable to studies in which physiological experimentation was to be extended over a considerable period of time. The constant flow method used by Hall 1 was modified for the present study. Hall measured the metabolism of many fishes over short periods of time. The present method is adapted for more detailed studies and provides for greater care of the experimental animals. Although Hall employed urethane to inhibit the movement of the fishes, Wieland (1915) states that the use of urethane causes the CO₂ threshold to be raised in the animals thus treated, and Winterstein (1914) concludes that O₂ consumption is decreased with the administration of urethane. Injection with urethane would have to be repeated after a 2-hour period, with consequent mechanical injury and metabolic disturbance to the fish; therefore Hall's method of controlling movement would not be applicable to protracted studies.

Twenty-eight fishes, 18 individuals of the large mouthed black bass, Micropterus salmoides (Lacepede), and 10 of the bluegill, Lepomis incisor (Mitchell), were used. Except in preliminary tests all experiments were carried out on fasting fishes, to obtain conditions more or less comparable with those prescribed for testing basal metabolism in humans. Twenty-four hours were allowed to elapse after the fishes were collected so that the intestine would be empty of fecal matter; each individual was then weighed, and placed in a fish jar in which it was to be tested (Fig. 1 B) for several hours before a series of determinations was begun.

Metabolic rate was measured in terms of cc. of oxygen consumed per kilo of body weight per hour. Oxygen determinations were made by the use of the Winkler method as described by Kemmerer, Bovard and Boorman (1924).