Seasonal Variations of Ciliate Protozoan Infection in Different Stages of Black Tiger Shrimp (Penaeus monodon)

Abstract

Aquaculture is sunshine sector and the culture of tiger shrimp (Penaeus monodon) generates huge earnings through exports. Diseases cause severe damage to the culture resulting huge losses to the farming community. Among the diseases, ciliate protozoan parasites pose a significant threat to the aquaculture of the Black Tiger Shrimp (P. monodon), often causing mass mortality and reduced yields. In the present research the seasonal distribution of Ciliate parasites (Acineta, Epistylis, Vorticella and Zoothammium) infections across various stages of P. monodon (Nauplii, Zoea, Mysis, Post-Larvae, Juvenile and Adult) and some selected physicochemical parameters of the water was studied. Samples were collected monthly across four hatcheries in the Andhra Pradesh coast of India from 2011 to 2012. The water parameters i.e. temperature, salinity, pH, and dissolved oxygen were recorded, and the parasites were identified. The pattern was distinctly seasonal, with the greatest prevalence occurring in the summer (pre-monsoon) months and ciliate infections evident in all life stages. Infection rates were high in post-larvae 23 days samples, with values recorded 66.6% in Pulicat Lake. Low infection rates were observed during autumn and winter. Also, some hatcheries, such as Gudur, demonstrated 55-70% infection rates, which was significantly higher relative to other hatcheries, such as Chirala. These findings emphasize the importance of ecosystem elements such as high temperatures in summer affecting the metabolism and moulting cycles of shrimp, as the cause of the outbreaks of ciliate protozoans. These results further emphasize the need for active monitoring and summer management strategies to reduce parasitic losses and improve productivity and sustainability of P. monodon aquaculture.