THE EFFECT OF TEMPERATURE AND PHOTOPERIOD ON THE RESPIRATORY METABOLISM OF RAINBOW TROUT (SALMO GAIRDNERI)

Abstract

Mid-winter spawning rainbow trout (Salmo gairdneri) were acclimated for a minimum of 43 days to one of four temperature-photoperiod conditions 16[degree]C-16L (hours daily photoperiod), 16[degree] C-8L, 8[degree] C-16L, 8[degree] C-8L. Oxygen consumption of the intact fish and of samples of liver, gill, and brain were measured at acclimation temperature. Brain showed complete metabolic compensation to temperature (QO2 at 8[degree] C = QO2 at 16[degree] C) and liver showed overcompensation (QO2 at 8[degree] C > QO2 at 16[degree] C). No compensation occurred in gill respiration. Total respiration showed partial temperature compensation. It is suggested that complete compensation in brain would maintain nervous co-ordination and motor conduction at optimal levels, thus permitting a large degree of temperature independence of locomotor activity. QO values of the tissue showed a trend for the 8L tissues to metabolize more rapidly than the 16L group, except for gill at 16[degree]C. Photoperiod did not significantly affect total metabolic rates, but in the larger fish (> 40 g) at 16[degree] C, the 8L group tended to show a higher metabolic rate than the 16L group.