Sediment selection in juvenile plaice and its behavioural basis

In the laboratory juvenile plaice Pleuronectes platessa (13–114 mm) were consistently found on the finest of four sediments after 24 h both in the light and the dark. Preference when assessed both by the fish's final position and by the amount of time it spent on each sediment agreed on 72% of occasions. Size did not affect preference, which was determined principally by a fish's ability to bury in a sediment. Burial reduces activity and thereby increases the time that fish spend on sediments in which they can bury. Activity level, which is dependent on light intensity and endogenous factors, therefore determines the degree of selectivity shown. Swimming duration and resting by the largest fish (71–114 mm) did not differ among sediments. Field experiments produced results similar to those obtained in the laboratory.