Oxygen consumption by the Cape rock lobster<i>Jasus lalandii</i>

Abstract

The metabolic rates of a wide size-range of the rock lobster Jasus lalandii (20–3 000 g wet mass) over a temperature range covering normal annual fluctuations (8–19°C) were studied, and this information was used to estimate the energy demands at population level. Over the studied temperature range and at standard rates of oxygen consumption, J. lalandii had a Q 10 value of 2,5. Plotted for five temperatures, the graph of oxygen consumption rates had a typical sigmoidal appearance, with a flatter response (Q 10 = 1,7) between 10 and 13°C, which coincides with the modal habitat temperature. At 19°C, the animals appeared stressed and showed an easing in respiration rate, with Q 10 = 1,4. Respiration is mass-dependent, metabolic rate being inversely proportional to body mass. Responses to a short-term drop in temperature of 5°C produce a rapid decrease in consumption rate of oxygen, with no undershoot occurring and with no suggestion of acclimation taking place. An increase of 5°C also induced a rapid response which resulted in an overshoot, followed by a gradual return over 2–5 days to the predicted rate, which could not be interpreted as one of acclimation. For a population of rock lobsters off Robben Island, north-west of Cape Town, at a mean annual temperature of 13°C, animals metabolize, on average, the equivalent of their body mass of carbon each year. This represents an irreversible energy loss to the biotic community and is equivalent to the oxidation of 26 g C·m−2·year−1.