Temperature and metabolic rate in sedentary fish from the Antarctic, North Sea and Indo-West Pacific Ocean

Abstract

Resting metabolic rate$(\dot V_{O_{2[rest]} } )$ was measured in demersal stages of the teleostNotothenia neglecta Nybelin from the South Orkney Islands, Antarctica, from 1985 to 1987. The relationship between$\dot V_{O_{2[rest]} }$ and body mass (Mb) conformed to the general relationship$\dot V_{O_{2[rest]} } = aMb^b$, wherea is a proportionality constant andb is the scaling exponent.$\dot V_{O_{2[rest]} }$ (mg O₂ h⁻¹) was found to scale toMb ^{(0.82±0.011)} in the summer (November to April, 1.6 to 1 850 g,n=56) and toMb ^{(0.76±0.013)} in the winter (May to October, 0.9 to 1 850 g,n=57) (values ofb are means ± SD). Although the scaling exponents were significantly different (P<0.01),$\dot V_{O_{2[rest]} }$ 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$(\dot V_{O_{2[max]} } :\dot V_{O_{2[rest]} } )$ 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 andMyoxocephalus scorpius) and the Indo-West Pacific (Paracirrhites forsteri, P. arcatus, Neocirrhites armatus andExallias brevis). Extrapolated values of$\dot V_{O_{2[rest]} }$ for the tropical species approached zero at 5 to 10°C. For a standard 50 g fish,$\dot V_{O_{2[rest]} }$ for the tropical species at 25°C was in the range 3.4 to 4.4 mg O₂ h⁻¹, compared with 1.3 mg O₂ h⁻¹ forNotothenia neglecta at its acclimation temperature. Thus, the maximum metabolic rate of sedentary tropical species at 24°C is likely to be 2 to 4 times higher than inN. neglecta at 0°C. This suggests that the energy available for sustained activity$(\dot V_{O_{2[max]} } - \dot V_{O_{2[rest]} } )$ is significantly lower in cold- than in warm-water fish.