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

Resting metabolic rate(V ˙ O 2[rest] ) (V˙O2[rest]) was measured in demersal stages of the teleostNotothenia neglecta Nybelin from the South Orkney Islands, Antarctica, from 1985 to 1987. The relationship betweenV ˙ O 2[rest] V˙O2[rest] and body mass (Mb) conformed to the general relationshipV ˙ O 2[rest] =aMb b V˙O2[rest]=aMbb , wherea is a proportionality constant andb is the scaling exponent.V ˙ O 2[rest] V˙O2[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),V ˙ O 2[rest] 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 ˙ O 2[max] :V ˙ O 2[rest] ) (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 andMyoxocephalus scorpius) and the Indo-West Pacific (Paracirrhites forsteri, P. arcatus, Neocirrhites armatus andExallias brevis). Extrapolated values ofV ˙ O 2[rest] V˙O2[rest] for the tropical species approached zero at 5 to 10°C. For a standard 50 g fish,V ˙ O 2[rest] V˙O2[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(V ˙ O 2[max] −V ˙ O 2[rest] ) (V˙O2[max]−V˙O2[rest]) is significantly lower in cold- than in warm-water fish.

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