Settlement of Iceland scallop Chlamys islandica spat in response to hydroids and filamentous red algae: field observations and laboratory experiments

Abstract

Sampling carried out in the Baie des Chaleurs, Gulf of St Lawrence, showed that newly settled Iceland scallop spat were not randomly distributed on the sea bottom. Twenty times more post-larvae were found on perisarcs of the dead hydroid Tubularis larynx than on live hydroids and red algae (another preferred natural substratum). Maximum densities, up to 300 spat g-1 (dry wt) of hydroids, were observed on a mooring line 2m from the bottom. Spat can resettle easily when dislodged from their substratum. Independent of origin, >60% spat preferred to resettle on dead rather than live hydroids, filamentous red algae (Ptilota serrata and Phycodrys rubens) or fishing line. They also preferred to resettle on the type of substratum to which they were previously attached. -from Authors