Effect of Acetic acid treatment on the control of non-indigenous ascidians in farmed Indian pearl oyster Pinctada fucata

Abstract

Control of biofouling has been one of the major challenges in pearl culture. Field experiments were performed to control the biofouling in farmed pearl oyster Pinctada fucata by treating the oysters first with 5% acetic acid at different time interval (2, 5, 10 min) and then kept for evaluation at three depths (1, 3, 5 m). The average total fouling biomass on oysters exposed for 2, 5, 10 min were 7.35, 6.97 and 6.49 g/oyster/month respectively, while control showed 10.56 g/oyster/month on completion of four months. Mortality of oysters were 60, 29, 14% at 10, 5 and 2 min exposure and control had only 7%. There was significant differences in total fouling biomass and mortality between the control and treatments (p<0.001). Results suggest that 2 min exposure of oysters in acetic acid and deployed at a depth of 3 m was found to be best for reducing biofouling as well as more effective in preventing the settlement of non-indigenous ascidians, especially Didemnum sp. The outcome of the present study may contribute to further optimise the current antifouling managements in pearl culture and fill the knowledge gap for farming practices and their management specifically with reference to the monitoring and cleaning procedures.