Activity patterns of abalone under experimental conditions

Locomotion behaviour of the abalone, Nordotis discus (Reeve), N. gigantea (Gmelin) and Sulculus aquatilis (Reeve), was observed for 5- to 10-day periods during the early summer and autumn from 1997 to 1999, Before sunset, the animals were individually put beneath each shelter situated on the flat concrete floor of indoor and outdoor tanks. For tracing of the locomotion path, a luminous rod was fixed on the animal's shell, Except for nonappearance, the locomotion behaviour showed leaving or homing; these ratios against each total observation according to each species were 70.0% and 16.7% in N, discus, 47.1 and 23.5% in N. gigantea and 57.6 and 24.2% in S, aquatilis respectively. Irrespective of species, recurrences to the home were frequently recognized during the locomotion. For the homing behaviour, its critical distance was approximately Im from the home. Moonlight did not completely restrain the abalone appearance from the home, though the appearance frequency during the period around the full moon was lowered and in some cases the time of initial appearance was retarded.