Control of Vibrio spp. in Shrimp Hatcheries Using the Green Algae Tetraselmis suecica

The Vibrio spp. are the most common and harmful shrimp pathogenic bacteria causing serious diseases of larval and postlarval stages in the hatchery. The Vibrio inhibitory activity of green algae Tetraselmis suecica has been reported in vitro (Austin and Day 1990).In these experiments, the inhibitory activity was assessed in vivo in a commercial shrimp hatchery of the white prawn Fenneropenaeus indicus. The concentrate of the algae was used as a food supplement for the broodstock and also as partial live larval feed in the larval rearing tanks. Results showed that use of algae resulted in significant reduction of Vibrio numbers in maturation and spawning tank water, broodstock gut contents, egg and nauplii samples. The spawning tank water Vibrio count showed a negative correlation with egg hatching rate. The algae when used in larval tanks were found to reduce Vibrio count in both rearing water and larval samples, resulting in improved nauplii 5 to postlarvae 1 survival. Rearing tank experiments with axenic algae proved that the inhibitory effect was by Tetraselmis and not by associated bacteria. Usage of this algae in the hatcheries will be advantageous as it suppresses the dominance of Vibrio spp. may be including the potentially pathogenic ones.