TEMPORAL PATTERNS OF MOVEMENT IN JUVENILE FLATFISHES AND THEIR PREDATORS - UNDERWATER TELEVISION OBSERVATIONS

Underwater television cameras were used to observe the movements of bottom-living animals in the intertidal and shallow subtidal zones of a sandy shore over sixteen 24-h periods in the summers of 1991 and 1992. Juvenile (0-group) flatfishes, predominantly Pleuronectes platessa L. with some Limanda limanda (L.), were only seen moving on the bottom by day, with most observed at high water and just before sunset. Their movements were directed offshore in the morning and onshore in the afternoon. They also tended to move onshore with the flood tide and offshore with the ebb. These fishes may use midwater swimming for inter-tidal migration by night because none was seen moving on the bottom at night. Potential predators of 0-group flatfishes, cod Gadus morhua L., crab Carcinus maenas (L.) and the brown shrimp Crangon crangon (L.), were most often seen moving on the bottom at night. Crangon, Carcinus and I-group flatfishes were seen in similar numbers in the subtidal and intertidal zones, while 0-group flat-fishes, cod and hermit crabs Pagurus bernhardus (L.) were seen much more frequently under the subtidal camera.