Spawning of kuruma shrimp [Penaeus japonicus] in a closed recirculating aquaculture system after eyestalk ablation

Using a closed recirculating aquaculture system including foam separation and nitrification units for kuruma shrimp Marsupenaeus japonicus, a spawning test was carried out in the limited space of the culturing tank (area, 1 square m). The female shrimp (average body weight 65 g) used in the test were unqualified for seedling production in the actual shrimp farm because they had a spermatophore but immaturity of their ovary. The nine females were treated with unilateral eyestalk ablation using a rubber tag and cultured in the individual cages set in the culturing tank. Ovarian development was visualized by employing a flashlight to distinguish the development ratio of ovary in the dorsal exoskeleton. All individuals in the system survived throughout the test period (15 days). Five individuals within 9 females spawned within 15 days. There were two individuals which spawned two to three times during the period. The average number of eggs in spawning was 5.1 x 10E4/individual. After the spawning test, the females reared in the system were judged white spot disease virus (WSDV) free by the method of loop-mediated isothermal amplification (LAMP). In the small-scale of closed recirculating system, it was verified that female shrimps could be spawned under virus-free conditions.