Growth and biometric relationships of the pearl oyster Pinctada fucata (Gould) on transplanting from the Gulf of Mannar to the Arabian Sea

Comparative studies were made on the growth and biometric relationships of the pearl oyster Pinctada fucata (Gould) Tuticorin stock at (Tuticorin (TST) – parent stock) transplanted from the Tuticorin Bay (8.7°N; 78.2°E) in the Gulf of Mannar along the Indian southeast coast to Kollam Bay (8.8°N; 76.5°E) in the Arabian Sea along the Indian southwest coast (Tuticorin stock at Kollam (TSK) – transplanted stock). At the time of transplantation, Kollam Bay did not have a native stock, however, within a year, the transplanted stock spawned and oyster spats were collected from within the farm (Kollam stock (KS) – progeny stock). The growth in dorso‐ventral measurement and total weight in Kollam Bay was 1.4–1.6 times and 3.1 to 6.8 times respectively greater than that observed at Tuticorin. Furthermore, at Kollam Bay, the thickness observed at the end of first year was similar to that obtained at the end of second year in Tuticorin. Both the TSK and KS had significantly higher instantaneous growth rates (IGR) than TST. All the stocks displayed significantly different biometric relationships. The increased growth in Kollam Bay is attributed to the almost double productivity in the Arabian Sea compared with the Bay of Bengal. It is concluded that in the case of P. fucata, the site and its interaction with environment are important determinants of growth and shell dimensions. The present study clearly indicates that the environmental conditions prevailing along the southeast Arabian Sea are congenial for the growth, gametogenesis, spawning and settlement of P. fucata larvae. In spite of strong monsoonal influences in the hydrology of Kollam Bay, the growth and reproduction of P. fucata stocks indicates its relative hardiness and ability to adapt to a changed environment.