Diurnal activity pattern of plaice and flounder (pleuronectidae) in aquaria

Abstract

Activity recordings of plaice and flounder in aquaria under natural conditions of illumination demonstrate that in the daytime there is a feeding period during which the activity is restricted to the bottom level, whereas there is much additional swimming at higher water levels during the night.

The registration technique with a balanced false bottom used by Harder and Hempel (1954) leaves the feeding activity on the bottom undetected. This accounts for the discrepancy between the predominantly nocturnal activity of plaice as registrated by these authors and the diurnal activity in the normal habitat as concluded from data derived from trawl catches and the gut content of caught fish. A tentative comparison is made between the behaviour of plaice and sole.