The effect of temperature and mass on routine oxygen consumption in the South African cyprinid fish <i>Barbus aeneus</i> Burchell

Abstract

Routine metabolism was measured for Barbus aeneus ranging in mass from 4.1 g to 520 g over the temperature range 9.5–26°C. The mean slope of the double logarithmic relationship between total oxygen consumption and mass was 0.69. The slope of the response of specific oxygen consumption to temperature increased with increasing mass. It is suggested that the lesser effect of temperature on specific oxygen consumption in smaller fish is because osmosis is a passive physical process, with a Q 10 in the range 1.1–1.4, while the Q 10 for biochemical processes is typically in the range 2–4. At lower temperatures a greater proportion of the total metabolism would therefore be devoted to osmoregulation. This would have implications for the energy balance of small fishes, since in these the ratio surface area: mass is greater and accordingly the proportion of total metabolism devoted to osmoregulation would be higher than in larger individuals.