Ocean sunfish’s ability to slow down body temperature cooling

A sunfish lying on the surface of the sea

The sunfish is an ectothermic fish and perform behavioural thermoregulation. According to a previous study on the behaviour of sunfish in the cooler northern region of Japan (Nakamura et al. 2015), sunfish moved back and forth between a cooler depth of 200 m and the warmer surface at intervals of several tens of minutes to forage at depth. The body temperature of the sunfish decreased at depth and recovered while at the surface. The warming rate at the surface was several times greater than the cooling rate at depth. This result has suggested that sunfish warmed up efficiently to shorten the recovery time of their body temperature.
  In this study, we attached bio-logging packages to three sunfish and released them in the warmer southern region of Japan. We found that the warming rate of the sunfish was similar to that of the previous study, while the cooling rate was larger. These results suggest that the sunfish in the previous study did not warm up efficiently at the surface but prevented heat loss when foraging in cooler depths. This ability allows the sunfish to take advantage of the deep-sea environment, which is cold but rich in food for sunfish.

 

Nakamura I, Yamada M (2022) Thermoregulation of ocean sunfish in a warmer sea suggests their ability to prevent heat loss in deep, cold foraging grounds. Journal of Experimental Marine Biology and Ecology, DOI: 10.1016/jembe.2021.151651
https://www.sciencedirect.com/science/article/pii/S0022098121001416

Reference
Nakamura I, Goto Y, Sato K (2015) Ocean sunfish rewarm at the surface after deep excursions to forage for siphonophores. Journal of Animal Ecology 84, 590-603

 

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