Physiological responses of the labrid fish Notolabrus celidotus to temperature change, found thermal compensation to be more advanced in cold environmental temperatures compared to warm environmental temperatures. N. celidotus was acclimated for 28 days to 8, 14 and 24ºC and metabolism, ventilatory and circulatory function, condition factor, swimming ability, thermal tolerance and hypoxia tolerance investigated.

N. celidotus acclimated to 8ºC almost achieved full thermal compensation, which resulted in, resting and maximum oxygen consumption not being significantly different to 14ºC acclimated fish. In contrast, N. celidotus acclimated to 24ºC achieved only partial or no metabolic thermal compensation. This resulted in high resting oxygen consumption and a reduced aerobic scope for activity, which had detrimental affects on other physiological parameters investigated.

Thermal compensation was achieved for the resting ventilation rate of the 8ºC acclimated fish, which is most likely needed in order to meet the high oxygen demands incurred by metabolic thermal compensation. No thermal compensation was achieved for any other ventilation rate or for heart rate, at any acclimation temperature. Thermal compensation at the level of heart and ventilation rate of the 24ºC acclimated fish, would have been limited by the lack of metabolic thermal compensation. A low condition factor of the 24ºC acclimated fish would also have occurred due to the lack of metabolic thermal compensation, which would have caused high-energy demands and the utilization of energy stores.

Thermal tolerance ranges shifted in the direction of temperature change for all acclimation groups, which indicates thermal compensation must have occurred to some degree at a variety of organizational levels. Swimming ability reflected metabolic thermal compensation, with the swimming ability of the 8ºC acclimated fish being similar to the 14ºC acclimated fish. In comparison, the 24ºC acclimated fish had a diminished swimming ability, which is likely to have occurred due to the reduced aerobic scope for activity of these fish and the low condition factor.

The findings suggest that the increasing temperatures associated with climate change will cause N. celidotus to migrate to cooler waters in order to survive. This response will have a large effect on New Zealand’s marine ecosystem as N. celidotus is abundant in New Zealand waters and is an important part of the food chain. Additionally, the response of N. celidotus may be an indicator of the response of other New Zealand species to climate change, which could cause huge upset to New Zealand commercial fisheries.