Oxygen utilization by fishes and other aquatic animals. 1

Abstract

A. Lowering of the temperature causes a reduction in the rate of oxygen consumption. In one case, while one lot of fishes consumed 78 per cent. of the available oxygen supplied at 12° C; a similar lot of fishes in water 4° colder consumed but 60 per cent. In a second case, a fish in water at 20° C. consumed 94 per cent. of the oxygen present while a similar fish at 3° C. consumed but 57 per cent. Breathing had ceased in this case but was resumed on return to warmer water.

B. It was noted that oxygen was consumed more rapidly in tall, narrow vessels of water than in broad shallow ones. Fishes moving about in shallow vessels of water tend to reaerate the same. In one experiment to test this, one lot of fishes in tall narrow vessels of water consumed 80 per cent. of the oxygen supply, while in the broad shallow water at the end of the same period, the analysis indicated a reduction of but 20 per cent. of the original oxygen supply.

C. Fishes kept in dark vessels apparently consume oxygen at a less rapid rate than those exposed to light. Thus in the light one fish consumed oxygen at the rate of 0.12 c.c. per gm. per hr. while in the dark the rate was D. 11 c.c. per gm. per hr. But there was no evidence as to rate of oxygen consumption being, less at night than in the daytime the rate being approximately the same.

D. Some forms show more resistance to low oxygen supply than others. This is particularly true of invertebrates. Respiration ceases altogether, and returns if the specimen is returned within certain time limits, to aerated water.