Spat production of the great scallop (Pecten maximus): a roller coaster1This review is part of a virtual symposium on current topics in aquaculture of marine fish and shellfish.

The great scallop ( Pecten maximus (L., 1758)) has been of interest for aquaculture in Europe since the early 1970s. Since then, a large part of the research and development has focussed on reproduction and early life stages to support hatchery production of spat. Results from the last two decades show that production stability is lacking and have followed a roller-coaster trend. Production strategy varies, but in general, broodstock are collected from the wild and conditioned to gonad maturity sufficient for successful spawning. Natural reproduction cycle varies between populations, which is a challenge to hatcheries aiming at stable year-round production. Larval survival was for many years dependent on addition of antibiotics until a flow-through culture was established, and seasonal variation may be caused by variation in gamete or seawater quality. Settlement, metamorphosis, and spat growth depend on healthy larvae and appropriate culture environment. For efficient spat production, the use of land-based nurseries is promising. Results show that mean yield of spat from eggs is less than 1%. The review concludes that the gap between results obtained in hatchery production and in experiments shows a great potential for production increase.