Antarctic fish's winter 'sleep'

The Antarctic cod puts itself into a state similar to hibernation for the winter, researchers have found, which is highly unusual for a fish. Scientists with the British Antarctic Survey (Bas) found Notothenia coriiceps lowers its metabolic rate during winter, saving energy.

As with hibernating mammals, the fish rouse themselves now and again from their dormant state for short periods.

Researchers suspect the "hibernation" is triggered by changes in sunlight.

The sea temperature varies by only about 2C between summer and winter, which is probably too small a difference to induce such a significant change in behaviour. "It appears the fish utilise the short Antarctic summers to gain sufficient energy from feeding to tide them over in winter," said Keiron Fraser from Bas.

"The hibernation-like state... is presumably a mechanism for reducing their energy requirements to the bare minimum. - bbc