Survival, growth and yield of competent great scallop (Pecten maximus) larvae were investigated during a full production season in a commercial hatchery in western Norway. Broodstock were collected from natural scallop beds and 12 groups were induced to spawn during the period December 2002 to July 2003. Larvae were reared on a large scale in 36 flow-through tanks (3500 l) at 17±1°C and continuously fed a mixture of five algal species produced in an indoor continuous-flow system. Large variations in larval performance between spawning groups and tanks were observed, but the results were as good as earlier results using the batch system and prophylactic addition of chloramphenicol. Growth from days 3-24 averaged 4.8 lm day )1 ±0.8 (sd) and survival 22.4%±21.8 (sd). Mean yield of day 3 larvae was 7.1%±10.0 (sd) and 26.6%±25.9 (sd) for those surviving to day 24. Yield was significantly correlated to larval survival. Larval success was related to initial larval density, algal concentration and season. It was found that the best production regime had an initial larval density lower than 6 ml )1 and algal concentration of less than 12 ll )1 regardless of season. Seventeen tanks met these criteria and produced a mean yield of 0.5 larvae ml )1 to settlement. Flow-through systems are currently regarded as the only feasible method for viable hatchery production of P. maximus larvae in Norway.

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.Résumé : L'aquaculture européenne s'intéresse au grand pétoncle (Pecten maximus (L., 1758)) depuis le début des années 1970. Depuis lors, une partie importante de la recherche et du développement s'est concentrée sur la reproduction et les premiers stades de vie afin de favoriser la production de naissains en culture. Les résultats des deux dernières décennies montrent qu'il manque une stabilité dans la production et que les tendances ressemblent à des montagnes russes. Les stratégies de production varient, mais généralement le stock reproducteur est récolté en nature et conditionné jusqu'à la maturité des gonades pour obtenir une fraie réussie. Le cycle de reproduction naturelle varie d'une population à l'autre, ce qui présente un défi pour les cultures qui visent une production stable à l'année. La survie des larves a dépendu pendant de nombreuses années de l'addition d'antibiotiques jusqu'à qu'on mette au point une culture avec système de circulation; la variation saisonnière peut être due à la variation dans la qualité des gamètes ou de l'eau de mer. La fixation, la métamorphose et la croissance du naissain dépendent de la santé des larves et de la présence d'un milieu approprié de culture. Pour une production efficace du naissain, l'utilisation de nourriceries en milieu terrestre est prometteuse. Les résultats indiquent que le rendement moyen du naissain à partir des oeufs est de moins de 1 %. Notre rétrospective conclut que l'écart entre les résultats obtenus par aquaculture et en laboratoire montre qu'il existe un fort potentiel pour l'accroissement de la production.[Traduit par la Rédaction]

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The mussel (Mytilus edulis) is successfully grown in aquaculture in Europe. Mussels are usually sold live and wet storage is becoming more common. In this study, oxygen demand and ammonia excretion were assessed at increasing water temperatures and different post-harvest situations. This information was used to calculate minimal flow rates per unit biomass of live mussels sufficient to keep oxygen above 5 mg L −1 or 50% saturation, and avoid accumulation of ammonia in commercial wet storage. In this study, rope-grown mussels were kept out of water for 8 h to simulate harvesting conditions and then re-immersed in holding tanks at 5, 10 and 15 • C. Oxygen and ammonia concentrations were measured immediately after mussels were re-immersed (0 h), after 6 h and then every day for 3 days. After this period, the mussels were again kept out of water for 48 h to simulate long-distance transport and once again re-immersed for the same period as before. In the first 6 h after re-immersion, the oxygen consumption was between 7.5 and 12.2 μmol g −1 h −1 (dry flesh) and after this period it decreased to a standard level of around 4.0 ± 0.9 μmol g −1 h −1 and was independent of temperature. There were no major differences in oxygen consumption between mussels having spent 8 and 48 h out of water at any of the subsequent water temperatures used for re-immersion. In contrast, the ammonia excretion showed greater differences according to temperature and time out of water. Ammonia excretion was lowest at 5 • C (<0.01 μmol g −1 h −1). The implications of these results for the industry and authorities are discussed considering the water flow rate, depuration specifications and energy costs.