Aquaculture International 8: 249–257, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands. Short communication Flow-through systems for culturing great scallop larvae SISSEL ANDERSEN 1∗ , GAVIN BURNELL 2 and ØIVIND BERGH 3 1 Institute of Marine Research, Austevoll Aquaculture Research Station, N-5392 Storebø, Norway; 2 Department of Zoology, University College, Lee maltings, Prospect Row, Cork, Ireland; 3 Institute of Marine Research, Department of Aquaculture, P.O. Box 1870 Nordnes, N-5817 Bergen, Norway (Received 20 March 2000; accepted 1 April 2000) Abstract. Rearing of great scallop (Pecten maximus L.) larvae was tested in static and flow- through systems in order to improve intensive rearing methods and avoid bacterial problems. The static systems were: standard 300 litre tanks (STD) and standard tanks supplied with an antibacterial agent (STD+A). The flow-through systems were: 500 l down-welling tanks (FLOW) and a 4700 l up-welling tank (SILO). Bacteral counts ranked the systems in the following order SILO < FLOW < STD+A < STD. In spite of low bacterial numbers, increased larval survival was not demonstrated in the FLOW system compared to the STD system. The highest survival on day 17 (>90%) and day 22 (52%) after fertilisation was obtained in the SILO system. The type of rearing system did not affect larval growth. Key words: bivalves, flow-through rearing systems, great scallops (Pecten maximus) Larvae of great scallops (Pecten maximus) are susceptible to high mortalities in intensive rearing, often associated with bacterial contamination (Comely, 1972; Nicholas et al., 1996). Factors such as high temperature, high host density and excess of nutrients may favour the proliferation of opportunistic pathogens. The conventional European system of batch culture of scallop larvae, including full exchange of water several times during the week, and feeding once or twice a day (Buestel et al., 1982; Cochard and Devauchelle, 1993; Taylor et al., 1994), results in high pulses of organic material, and an unstable microbial environment, which is commonly controlled by prophy- lactic use of antibacterial agents (Robert et al., 1996; Torkildsen et al., 2000). In addition to counteracting the pathogens by antibacterial agents and disin- ∗ To whom correspondence should be addressed at: tel: +47 56 18 03 42; fax: +47 56 18 03 98; e-mail: sissel.andersen@imr.no