![]() Almost 80 percent of the particles are smaller than 30 µ. ![]() The spat diets, which are not algae-based and contain various natural ingredients, are dry powders that must be reconstituted with water prior to administration. Priority was given to the development of spat diets, since algae consumption is particularly high at the nursery stage. Because the nutritional requirements are very different between oysters, scallops, mussels, and clams, the diets are species-specific. New formulationsĪ range of formulated diets recently developed by INVE Technologies addresses the nutritional needs of bivalves with alternatives to algae. Most of the current alternative diets – such as spray-dried microalgae, microcapsules, yeast- or flour-based diets, lipid microspheres, and emulsions – can not fully replace the live microalgae, but are very useful as partial or backup diets. Furthermore, algae cultures often vary in nutritional value and are subject to seasonal growth patterns and contamination.īecause of the above problems, researchers and culturists are looking for low-cost alternatives. Algae production comprises up to 30 percent of hatcheries’ operation costs. In 1992, Coutteau and Sorgeloos identified the mass production of live algae as a major bottleneck in bivalve hatcheries and nurseries. Bivalves are often fed multispecies algal diets, since they usually support better growth and development than single-species diets. In France, for example, 15 to 20 percent of Crassostrea gigas oyster spat is now produced from hatcheries.Īt present, the hatchery rearing of bivalves generally relies on the mass production of microalgae selected based on their mass-culture potential, cell size, digestibility, and overall food value. The percentage of hatchery-produced animals seeded compared to those caught from wild sources is increasing accordingly. Trials conducted with European flat oysters, Japanese oysters and blue mussels Spat from a nursery was stocked in a flow-through downweller system for the Mediterranean mussel trial.ĭuring the last 20 years, the number and size of bivalve hatcheries has dramatically increased to complement declines in wild fisheries and ensure a more consistent, higher-quality supply of material for producers and genetic improvement purposes.
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