Field performance of hatchery produced Asian green mussel, Perna viridis (Linnaeus, 1758) and strategies to optimise its farming

Abstract

This study evaluates the field performance of hatchery produced Asian green mussel, Perna viridis (Linnaeus, 1758) seed across three estuarine sites viz., Ashtamudi, Neendakara, and Vellimon in Kollam District, Kerala, south India, under varying stocking densities. Juvenile spat with an initial mean shell length ranging from 9.3 to 12.6 mm reached commercial harvest size (50.8-82.9 mm shell length) within 6-13 months after deployment under grow-out conditions. During the first three months, specific growth rates peaked at 2.69% day^-1 at Ashtamudi, 3.87% day^-1 at Neendakara, and 3.71% day^-1 at Vellimon, indicating rapid initial adaptation to field conditions. In the 13-month Ashtamudi trial, lines stocked at 2,000 seeds m^-1 produced an average yield of 33.4 kg m^-1 and a final shell length of 82.9 mm; however, the overall SGR was lowest (0.54% day^-1) because relative growth declined as mussel biomass increased overtime. Reducing the stocking density to 1,000 seeds m^-1 at Ashtamudi increased the overall SGR to 0.94% day^-1 but more than doubled the final survival rate from 37.5 to 77.02%. Among the short-term trials (6 months), fastest growth (8.7 mm per month) was recorded at Neendakara, yielding a final shell length of 70.4 mm with a final survival rate of 29.2%. In contrast, Vellimon experienced severe predation because protective sleeve net was not used, resulting in a low final survival rate of 16.79%, despite a steady specific growth rate of 0.91% day^-1. These results show that small hatchery produced seed requires effective predator protection to achieve higher field survival, unlike larger and more resilient wild-caught seed, traditionally used in mussel farming. Overall, integrating hatchery seed production with optimised stocking densities, seasonal harvesting schedules, and predator exclusion netting, offers a practical strategy to stabilise and expand commercial marine bivalve aquaculture along the south-western coast of India.

Keywords: Hatchery seed, Bivalve aquaculture, Stocking density, Specific growth rate (SGR)