Biometric relationships of the black winged pearl oyster, Pteria penguin (Roding, 1798) from Andaman and Nicobar Islands

The dimensional biometric relationships including that of length-weight was studied in the black winged oyster Pteria penguin , which is a candidate species for mariculture. During the life span of the winged oysters, growth in length and weight was initially 40-100 mm dorso-ventral measurement (DVM), positively allometric and subsequently became isometric (100-160 mm DVM) and finally reverted back to allometry (160-220 mm DVM). This is attributed to the increase in visceral mass of animals corresponding to gonadal maturation during the size range 100 - 160 mm DVM. In larger sized P. penguin , increase in shell length is more predominant as evidenced by large proportion of non-nacreous layer at the outer edge of the shell. There was no parallel increase in visceral mass resulting in allometry. All dimensional relationships were positive in relation to DVM; however the relationship between DVM and hinge length did not show significant R2 values (p>0.05) in all the size groups. This was mainly because, the tips of the hinge and ear were found to be broken at both the ends. Therefore, notch length is proposed as a better predictor of DVM in large hinged pterid oysters. Unlike other pterid pearl oysters, the thickness - DVM ratio showed a decline with size, indicating that bead seeding programmes can be initiated at early stages.