Comparison of growth performance and survival of clam Meretrix meretrix in Hapa, Plastic Bag, and Seabed-based culture methods in the southeast coast of Bangladesh

Abstract

The Asiatic hard clam Meretrix meretrix represents a valuable bivalve resource in coastal Bangladesh. This study evaluated the growth and survival of Meretrix meretrix cultured over 180 days period (January–June 2024) at two unique coastal sites on the southeast coast of the Cox’s Bazar Reju Khal and Chowfaldondi using four culture systems hapa, floating bag, seabed fencing, and seabed covering. Clam Meretrix meretrix seeds were collected from natural beds and stocked at method-specific densities. Monthly measurements of shell dimensions, total weight, and mortality were recorded alongside key water quality parameters including temperature, salinity, dissolved oxygen, pH, turbidity. Results showed significant differences (p < 0.001) in growth and survival among culture systems and between sites. Hapa culture yielded the highest growth rates across all shell dimensions and total weight, attributed to effective predator exclusion, enhanced water circulation, and improved phytoplankton access. Floating bag systems exhibited the lowest growth and survival, primarily due to severe biofouling by barnacles (Balanus spp.), green mussels (Perna viridis), and oyster spat (Crassostrea spp.) which restricted water flow, reduced oxygen availability, and increased interspecific competition. Seabed fencing and covering systems provided intermediate performance, benefiting from natural substrate conditions but remaining susceptible to partial predator intrusion and environmental variability. Survival rates were highest in fencing at Reju Khal and lowest in floating bags at the same site. Correlation and PCA analyses indicated that dissolved oxygen, salinity, and moderate turbidity were key drivers of growth and survival. These findings demonstrate that suspended hapa systems offer the most favorable conditions for M. meretrix growth, while bottom fencing provides better survival in predator-rich environments. The results highlight the need for site-specific culture strategies that integrate hydrodynamic conditions, fouling management, and predator control to optimize clam mariculture in Bangladesh.