Effects of Severe Hypoxia on Carbohydrate Energy Stores and Metabolism in Two Species of Fresh-Water Fish

Abstract

Bluegill sunfish, Lepomis machrochirus, and cutthroat trout, Salmo clarki, were exposed to a rapidly declining O2 tension for a period of time sufficient to just cause loss of equilibrium in the fish. During recovery from the stress, measurements of O2 uptake, blood lactate, blood glucose, liver glycogen, and muscle glycogen were made at fixed intervals of time. Hypoxia caused an immediate rise in blood lactate and O2 uptake in both species, but the trout showed the greatest increases. This suggests a greater degree of O2 debt in the latter, even though the stress routine used in this species was not as prolonged. A delayed peak in the blood lactate observed in the trout, but not in the bluegill indicated a possible impairment of circulatory function in the trout. The blood lactate returned to normal after 2 and 5 hr. in the bluegill and cutthroat, respectively. The return of the O2 uptake to control levels required 8 and 10 hr., respectively. An immeadiate mobilization of the carbohydrate stores occurred during the stress in both the bluegill and trout. The blood glucose concentration rose greatly in the bluegill but not in the trout.