Influence of water temperature on demand-feeding rhythms in sea bass

Under natural environmental conditions, sea bass feeding rhythms are nocturnal in winter and diurnal during the rest of the year. Increasing water temperature from 22 to 28 degrees C or decreasing it to 16 degrees C had little effect on the dual feeding behaviour of sea bass. An 8 : 16 LD photoperiod with low temperature or 16 : 8 LD with high temperature also failed to change the diurnal/nocturnal behaviour of sea bass. In conclusion, sea bass Feeding rhythms did not follow passively the manipulated environmental factors simulating summer and winter conditions in the laboratory, which suggests an endogenous circannual control of the seasonal phase inversion. (C) 1999 The Fisheries Society of the British Isles.