Movement and size stucture in a poulation of the blue starfish Linckia laevigata (L.) at Lizard Island, Great Barrier Reef

Abstract

On a patch reef surrounded by sand, the movements of L. laevigata conformed to Underwood's random walkmodel in most respects except that animals navigated unidirectional paths across the reef. At the edge of the reef, animals either turned back onto the reef or moved away across the sand, and this behaviour was studied in translocation experiments. When released on sand, L. laevigata navigated randomly distributed unidirectional paths. at speeds 10-20 times faster than on the reef. In this way, animals could migrate between patch reefs inhabited by L. laevigata of different sizes. Larger animals usually lived in deep water (≥ 10 m), but significant size differences were also found between adjacent patch reefs and were tentatively ascribed to variations in availability of food. Mean arm length of 26 animals starved in an aquarium for 1 week decreased from 115.4 to 108.5 mm, indicating that body size may change when L. laevigata migrates between patch reefs.