Zooplankton cultivation and prawn seed-production in an artificial ecosystem

The cultivation experiments were conducted in two parts: (1) zooplankton cultivation in a heterogeneous system as fundamental research (Experiment I); (2) prawn seed-production in a homogeneous system as applied research (Experiment II). In Experiment I, several types of apparatus were designed in order to study a feedback system for cultivation of zooplankton (Brachionus plicatilis andTigriopus japonicus). A 550-1 round transparent tank was used for reserve culture, A 150-1 zigzag stream unit was made of vinyl plates, and connected with the reserve culture tank. In both cases, the water was re-circulated 20 times a day by an airlift pump. A tower-decomposer tank and two blowing cultivators were specially designed for promoting energy-flow. During a 140-day experiment, total wet weight of feed and harvest were 4817 g of yeast and 4308 g of zooplankton, respectively. The rate of food conversionwas 89.4% in terms of wet weight and 33.6% in dry weight. In Experiment II, a 2500 m3-hatchery tank with movable aerators and airlift circulation systems was contructed to maintain an artificial ecosystem for rearing of the prawnPenaeus japonicus. Feeding rate in the 2500 m3-tank was 10.8% lower than that in the 200 m3-tank, but growth rate in the former was 10.6% higher than in the latter.