BACTERIA AS BIOCONTROL AGENTS FOR REARING LARVAE OF THE CRAB PORTUNUS-TRITUBERCULATUS

Bacterial strain PM-4, isolated from a crustacean culturing pond, improved the growth of crab (Portunus trituberculatus) larvae and repressed the growth of Vibrio anguillarum in seawater. PM-4 was cultured in a large quantity and was added daily for 6 d to 200 m3 of seawater used for culturing crab larvae. Initial bacterial density in the crustacean culture water was 10(6) cells/mL. When bacteria increased to more than 10(7) cells/mL (at crab larval growth stage zoea II), the protozoan population, primarily flagellates, grew rapidly and reduced bacterial numbers to 10(6) cells/mL. Among the bacterial assemblages monitored, added PM-4 dominated the bacterial populations, i.e. Vibrio spp. numbers decreased or even became undetectable in seawater. Production of crab larvae was greatly increased by adding bacterial strain PM-4 to their culture water.