Growth and mortality parameters of Turbinella pyrum (Linnaeus, 1758) exploited off Thoothukudi, south-east coast of India

The sacred chank, Turbinella pyrum is exploited throughout the year along Thoothukudi coast. The life span of T pyrum was estimated at about 13 years. The growth was observed to be high in the first three years of age, after which the individual attains maturity. Seasonal variation was found to have significant impact on the growth of T. pyrum and reduced growth was observed during the north-east monsoon months i.e., October and November. The growth coefficient (K) was 0.27 which indicates T pyrum as a slow growing species. The total instantaneous mortality rate (Z) was estimated as 1.73. The fishing mortality (1.33) was found to be more than three times of natural mortality (0.39) for this species, inferring their over-exploitation along Thoothukudi coast. The minimum size at first capture for this species should be fixed above 140 mm shell length (or 70 mm maximum shell diameter) to avoid recruitment overfishing. The chank fishing should be regularized to conserve this precious resource.