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Oyster spat production7/5/2023 ![]() (1969) reported the commercial feasibility of using treated collectors, this practice does not appear to have been widely employed.Ĭollectors used in France and some other European countries for the European flat oyster and the Portuguese oyster generally consist of semi-cylindrical ceramic roof tiles (10–12cm in diameter and 30 cm long), stacked in pairs (fig. ![]() It has been reported that shells treated with highly chlorinated benzenes, such as polystream, collected about two or three times as many oyster spat as untreated ones, and fouling and drilling of young oysters were significantly reduced (MacKenzie et al., 1961). For example, the European oyster seems to have a preference for materials containing calcium carbonate, whereas the American oyster may settle on any hard surface, including wood, plastic or glass. Though the main criteria in selecting the type of collector are easy availability, ease of handling and the surface area offered for the attachment of spat, the larvae of some species appear to exhibit preferences for certain types of substrates. As mentioned earlier, different types of collectors are in use, and they may be placed on the bottom or on raised structures. Generally, spawning occurs at temperatures of 15–20☌ in summer and autumn, but tropical species spawn throughout the year at higher temperatures.Īs well as the time and place of spat collection, the type of spat collector used is also of importance. Regular examination of plankton in the area will help to determine the actual time and place of spat-fall. Early setting of the spat collectors will result in the substrate becoming covered with fouling organisms, whereas late setting may result in poor collection of spat. Even though spat may settle at a wide range of depths, their survival is greatest in the intertidal zone, relatively safe from predators. For successful spat collection, suitable collecting devices have to be set in the proper place at the proper level and time. There is considerable variation in the time and abundance of spat-fall in any area, depending on a number of environmental factors including temperature and salinity. ![]() Countries like Japan export large quantities of seed oysters to other oyster-growing countries. Similarly, hatchery production of seed oysters is a separate specialized activity, and oyster farmers often start their operations with purchased seed. As spat-fall often occurs in areas away from environments suitable for oyster growing, the collection, transport and sale of oyster spat has developed into a separate industry. Oyster larvae normally settle in sites with low current velocities, but these areas may not be rich in plankton and so may not be conducive to good growth rates. Though the value of and need for hatchery-produced seed oysters are well recognized, it would appear that production costs have stood in the way of wider application of this technique. ![]() Methods for hatchery production of seed oysters have been developed and are being practised on a commercial scale by a small number of producers. As stated earlier, most present-day production of oysters is from collected wild spat. ![]()
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