Population characteristics of Villorita cyprinoides in Vembanad Lake, India

Abstract

ABSTRACTKrishna AV, Ammini P. 2017. Population characteristics of Villorita cyprinoides in Vembanad Lake, India. Lake Reserv Manage. 34:130—140.The Vembanad Lake system (VLS), the largest Ramsar site in India, faces a major ecological crisis because of reclamation. The lake ranks first in the production of the black clam (Villorita cyprinoides). In this study, we investigated the distribution patterns of V. cyprinoides, and reports that the central region of the VLS sustained the highest population density of the black clam. The average density of black clams ranged from 10 to 15,558 individuals/m2, with average sizes ranging from 2 to 40 mm. The average size at maturity was 20 mm. Further, we employed the use of population parameters as a tool to determine their exploitation status in the VLS. The rate of exploitation (E) of V. cyprinoides (0.763) was higher than the maximum exploitation rate (Emax; 0.529), clearly suggesting its overexploitation in the central region. This finding corroborated well with the size distribution analysis indicating that the legal harvestable size of 20 mm was the lowest size fraction in the sediment samples. Although population parameter tools have been used for many fish and shellfish species in the past, our study, the first on black clams in Indian waters, suggest that V. cyprinoides is overexploited in the central region, and conservation measures should be considered. Further, the study demonstrates the utility of population parameters, such as the rate of exploitation, for identifying zones within an ecosystem that warrant conservation for sustainable exploitation of fisheries resources.