Performance of a closed recirculating system with foam-separation and nitrification units for intensive culture of Japanese flounder

Abstract

Rearing experiment of Japanese flounder Paralichthys olivaceus was conducted with two different culture systems, a closed recirculating system having a foam-separation unit and a flow-through system in which natural seawater was continuously supplied. The closed recirculating system consisted of a fish tank of 1 m3 in water volume, foam-separation and nitrification units, pH and temperature controlling units, and a circulation pump. A key feature of this system is the foam-separation unit, which is equipped with an air inhalation-type aerator that vigorously injects numerous fine bubbles into the rearing water. Fish were fed commercial pellet diet for 90 days. The survival rate of fish was 93.5%, and the gross weight of fish increased from 28.4 kg to 50.0 kg during the experiment in the closed recirculating system without the effluent. In the flow-through system, the survival rate was 98%, and the weight increased from 33.8 kg to 64.1 kg. Based on these results, intensive aquaculture can be achieved with the closed recirculating system.