Ecofriendly onshore marine pearl culture - an overview

The onshore marine pearl culture technology developed by CMFRI at Visakhapatnam has been taken up on a commercial scale in the vicinity of Visakhapatnam. Hatcheries for the pearl oyster Pinctada fucata have been established. The pearl oysters were grown in cement tanks of 75t capacity from 5 mm to 50 mm DVM. The growth rates of pearl oysters fed with different species of diet Chaetoceros, Nanochloropsis and Isochrysis at different cell concentration showed wide variations. The growth rate of oysters reared at a density of 100 nos. /sq. m is better compared to that at higher densities. The depth of seawater and rate of water exchange per day have been standardized. Raw seawater filtered through a specially designed slow sand filter is being used in hatchery and culture tanks. The filtered seawater is directly used for all purposes without any treatment with chemicals or antibiotics. Usage of chemicals is undesirable even for cleaning purposes. The algal cell concentration up to 1.2 million/ml was achieved on a sustained basis in outdoor mass culture tanks. Use of only live feed and avoiding chemicals make this technology ecofriendly. Severalfactors related to growth and maintenance of hygiene of pearl oysters in onshore culture tanks are discussed