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3.1. Introduction

Although Brachionus plicatilis was first identified as a pest in the pond culture of eels in the fifties and sixties, Japanese researchers soon realized that this rotifer could be used as a suitable live food organism for the early larval stages of marine fish. The successful use of rotifers in the commercial hatchery operations of the red sea bream (Pagrus major) encouraged investigations in the development of mass culture techniques of rotifers. Twenty five years after the first use of rotifers in larviculture feeding several culture techniques for the intensive production of rotifers are being applied worldwide. The availability of large quantities of this live food source has contributed to the successful hatchery production of more than 60 marine finfish species and 18 species of crustaceans. To our knowledge, wild populations of rotifers are only harvested in one region in the P.R. China, (i.e. the Bohai Bay saltworks) where Brachionus plicatilis is used as food in local shrimp and crab hatcheries. The success of rotifers as a culture organism are manifold, including their. planctonic nature, tolerance to a wide range of environmental conditions, high reproduction rate (0.7-1.4 Moreoever, their small size and slow swimming velocity make them a suitable prey for fish larvae that have just resorbed their yolk sac but cannot yet ingest the larger Artemia nauplii. However, the greatest potential for rotifer culture resides, however, is the possibility of rearing these animals at very high densities (i.e. densities of 2000 have been reported by Hirata, 1979). Even at high densities, the animals reproduce rapidly and can thus contribute to the build up of large quantities of live food in a very short period of time. Last, but not least, the filter-feeding nature of the rotifers facilitiates the inclusion into their body tissues of specific nutrients essential for the larval predators (i.e. through bioencapsulation; see further).

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