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 °C–16L (hours daily photoperiod), 16 °C–8L, 8 °C–16L, 8 °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 ([Formula: see text] at [Formula: see text] at 16 °C) and liver showed overcompensation ([Formula: see text] at [Formula: see text] at 16 °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.[Formula: see text] values of the tissue showed a trend for the 8L tissues to metabolize more rapidly than the 16L group, except for gill at 16 °C. Photoperiod did not significantly affect total metabolic rates, but in the larger fish (> 40 g) at 16 °C, the 8L group tended to show a higher metabolic rate than the 16L group.