Parasitic Study of Indian Major Carp, Labeo rohita (Hamilton, 1822) in Selected Districts of West Bengal, India

Abstract

The present work was conducted to isolate and identify different parasites from Indian Major Carp (IMC) Catla catla. During the study period the severity of infection and Parasitic Frequency Index (PFI, %) were also estimated in terms of months, seasons and length groups of fishes. For the investigative purpose different districts of West Bengal were selected considering the potential of fishery resources. Approximately 300 fishes were observed during the entire period of observation. The parasite infested fishes were found to suffer mainly from respiratory manifestations, blackness of the skin and mortalities. The isolated parasites were Myxobolus, Thelohanellus, Trichodina, Dactylogyrus, Gyrodactylus, Nematodes, Argulus, Lernea and Chilodonella species. Besides these, developmental stages of different parasites were also found. Among these parasites Myxobolus, Dactylogyrus and Gyrodactylus showed the highest prevalence in winter. Remaining all parasites was found to be more during spring season. The 1-30 cm length group fishes were found to be more infested with the parasites compare to 30.5-40 cm length groups. INTRODUCTION Freshwater aquaculture mainly depends on carp culture practices that account 80% of total inland fish production and have proved sustainability at different levels of production over the years. Though the country possesses a large number of potential cultivable carp species, it is only the three Indian Major Carp i.e. catla (Catla catla), rohu (Labeo rohita) and mrigal (Cirrhinus mrigala), that contribute a lion's share with production of over two million tonnes. West Bengal being a 'rice-fish society', the State is highly significant historically, geographically and strategically since long past. The state has 37% of pond resources in India of which 70% are utilized for fish culture producing 1 to 3 million tonnes of freshwater finfish per year of the total 2.76 lakh hectares of impounded water area, about 70-79% is presently under fish culture.