DIFFERENCES IN REPRODUCTIVE ECOLOGY IN NATURAL AND TRANSPLANTED POPULATIONS OF PECTEN-MAXIMUS - EVIDENCE FOR THE EXISTENCE OF SEPARATE STOCKS

The seasonal reproductive and storage cycles of scallops, Pecten maximus (L.), transplanted as juveniles into the Bay of St. Brieuc, Brittany, from Scotland and from the Bay of Brest, were compared with the cycles of similar scallops in their areas of origin and with those of native St. Brieuc scallops. Major features of the reproductive cycle of the transplanted scallops remained unchanged from those of their areas of origin, indicating that genetic factors played a major role in controlling this cycle. In contrast, environmental factors apparently played the dominant role in determining events in the storage cycle. The results provide strong evidence, based on reproductive physiology, for the existence of partially genetically separated stocks within the European distribution of this scallop.