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SCALLOPS anyone? L iz and Graeme Clarke of Crail Bay Aquaculture Ltd have a special love for scallops. Last summer they asked Cawthron to produce scallop spat in the Glen hatchery for on growing trials on at their farms. At the same time Neil de Jong was keen to do an MSc project relevant to scallop farming in New Zealand under the supervision of Associate Professor Andrea Alfaro at the Aquaculture Biotechnology Group of AUT. Although scallop spat is not yet on Cawthron's 'menu', it did not take much to convince the boss that we should accommodate the Clarkes and a keen student. We had no experience with scallop larval rearing but it had been described for overseas species. We also had advice from Sissel Andersen in Norway and our own Aditya Kesarcodi-Watson who had just returned from working with the European King Scallop in France. In addition, our experience with mussels, oysters and geoduck gave us some confi dence to proceed with this experiment. Unfortunately we started too late in the natural spawning season so the brood-stock obtained from the Sounds was past its best. On February 16 we managed to spawn some animals, and two days later we counted about one million larvae. These larvae responded well to rearing methods similar to those we routinely use for mussels. On day three the larvae were 95µm wide and happily feeding on micro- algae. At 17 degrees celsius they grew 6µm per day. From day 21 onwards the larvae got ready for settlement, and on day 29 we had beautiful post-larvae with gills and a long foot, crawling at great speeds. We offered them coir for settlement but many preferred to settle on the side of the tank. Eight weeks after spawning we transferred the two to three millimetre spat to the nursery. The associated change of environment and food conditions may well have been the reason for the mortality we observed at that stage. However, the survivors managed to get through winter temperatures as low as fi ve degrees celsius and measured 23mm on September 9, and 27mm on September 18. Our fi rst attempt at producing scallop spat did not deliver the numbers Liz and Graeme were hoping for, but we still count it as a success: we proved that spat of the New Zealand scallop can be produced with methods that we are familiar with. These methods are suitable for industrial scale hatcheries. Of considerable note was the success we achieved in the high-density fl ow-through larval systems (over 200 larvae per mL). Only low density (three larvae per mL) fl ow-through systems have been reported in the literature before now, and scallop larval rearing is viewed around the world as more diffi cult than the rearing of other mollusc larvae. We have also identifi ed areas that would require more work should there be signifi cant interest in scallop farming: broodstock conditioning, optimal larval rearing temperature and diet, a simple settling system and a safe nursery system. The scallop grows naturally in many of our sheltered coastal areas suitable for shellfi sh farming. It would only take a few scallop farms the size of a standard mussel farm to produce a sustainable crop of considerable value. No doubt there will be a few mishaps and unforeseen problems along the way to building a successful industry. Scallop farming BY HENRY KASPAR (CAWTHRON INSTITUTE) AND NEIL DE JONG (AUCKLAND UNIVERSITY OF TECHNOLOGY) 7 month old spat, up to 23mm wide may not be as assured as mussel farming in economic terms, however we won't know unless we try. We thank Liz and Graeme Clarke for their generous support of this project. RESEARCH, CONSULTING AND LABORATORY ANALYSIS Aquaculture research Aquaculture impact assessments and consents Biosecurity and pest management plans IANZ accredited seafood laboratory Fisheries assessments and management systems Adaptive management plans CAWTHRON INSTITUTE Ph +64 3 548 2319 info@cawthron.org.nz www.cawthron.org.nz NOVEMBER/DECEMBER 2012 ■ NZ AQUACULTURE ■ 7 VIPP.AC4 45