TEMPERATURE AND METABOLIC-RATE IN SEDENTARY FISH FROM THE ANTARCTIC, NORTH-SEA AND INDO-WEST PACIFIC-OCEAN

Resting metabolic rate (V(O2)[rest]) was measured in demersal stages of the teleost Notothenia neglecta Nybelin from the South Orkney Islands, Antarctica, from 1985 to 1987. The relationship between V(O2)[rest] and body mass (Mb) conformed to the general relationship V(O2)[rest] = a (Mb(b), where a is a proportionality constant and b is the scaling exponent. V(O2)[rest] (mg O2 h-1) was found to scale to Mb(0.82 +/- 0.011) in the summer (November to April, 1.6 to 1850 g, n = 56) and to Mb(0.76 +/- 0.013) in the winter (May to October, 0.9 to 1850 g, n = 57) (values of b are means +/- SD). Although the scaling exponents were significantly different (P < 0.01), V(O2)[rest] was similar in the juvenile stages of summer- and winter-caught fish matched for body mass. The effects of activity on oxygen consumption was studied using a Brett respirometer. Adult stages had a factorial aerobic scope for activity (V(O2)[max]:V(O2)[rest]) of 5.7, which is similar to that reported for demersal fish from temperate latitudes. The effects of temperature on resting metabolism was investigated in fish with similar sedentary lifestyles from the North Sea (Agonus cataphractus and Myoxocephalus scorpius) and the Indo-West Pacific (Paracirrhites forsteri, P. arcatus, Neocirrhites armatus and Exallias brevis). Extrapolated values of V(O2)[rest] for the tropical species approached zero at 5 to 10-degrees-C. For a standard 50 g fish, V(O2)[rest] for the tropical species at 25-degrees-C was in the range 3.4 to 4.4 mg O2 h-1 compared with 1.3 mg O2 h-1 for Notothenia neglecta at its acclimation temperature. Thus, the maximum metabolic rate of sedentary tropical species at 24-degrees-C is likely to be 2 to 4 times higher than in N. neglecta at 0-degrees-C. This suggests that the energy available for sustained activity V(O2)[max] - V(O2)[rest]) is significantly lower in cold- than in warm-water fish.