Settlement of the Commercial Scallop, Pecten fumatus (Reeve) 1855, on Artificial collectors in Eastern Tasmania

The settlement of the commercial scallop, Pecten fumatus (Reeve) 1855, in artificial collectors was monitored on the east coast of Tasmania over a I-year period using spat collection techniques similar to those practised in Japan. Major spat settlement occurred in mid-late September but small irregular settlements were observed in late spring and early summer. Information on settle- . ment obtained in the first 2 years of the study was successfully applied in the collection of large quantities of scallop spat during the later years of the study. The number of settled scallop spat and growth of the spat varied with depth. Maximum settlement occurred at depths of 16-22 m, with a decrease in numbers towards the surface and the seabed (depth, 31 m) . Growth of scallop spat also varied with depth. Scallops in collectors near the surface grew faster than those in deeper water, the most noticeable change in growth occurring at depths between 16 and 20 m. A considerable percentage (up to 62% ) of settled spat were lost from the larger-mesh collectors and most losses occurred when spat detached their byssal threads in late November-mid-December. Further losses are attributed to fish predation and competition with colonising ascidians. Major colonising groups apart from scallops included brown and filamentous algae, ascidians, bryozoans, crabs, shrimps, gastropods, bivalves and fish.