Antarctic fish live in an environment with high seasonality, where levels of sunlight in the summer are up to 24 hours a day and in total darkness during the winter. Fish were monitored to determine if they show any sign of a classical circadian rhythm in a laboratory setting by videotaping them continuously for a period of 3-5 days and recording the level of activity. Fish were also monitored for ... activity levels by constantly measuring oxygen consumption for periods of 3-5 days. Samples of otoliths of fish were collected to determine if these Antarctic fish show daily growth rings. Samples of brain tissue were also collected and analysed using molecular techniques to determine whether Antarctic fish possess and produce the molecular clock proteins necessary for maintenance of circadian rhythms.