Survey of parasites of two fish species (Tilapia zillii and Clarias gariepinus) in Ase River Catchment, Delta State, Nigeria.

Tropical freshwater fishes such as Tilapia zillii (T. zillii) and Clarias gariepinus (C. gariepinus) serve as definitive/transport or intermediate host in the developmental cycle of many species of protozoan, metazoan and crustacean parasites[1]. Parasites are invertebrate organisms; some are free-living and can become opportunistic parasites while the obligate parasites require hosts for their survival and reproduction. Both opportunistic and obligate parasites are found in fish hosts but most parasitic diseases in fish are generally caused by obligate parasites[2]. In fisheries, some parasites may be highly pathogenic and contribute to high fish mortalities and economic losses or threaten the abundance and diversity of indigenous fish species[3,4]. T. zillii and C. gariepinus are the most common sources of protein for humans and other animals in the tropics[5-7]. Fish interacts with the various levels of food chain and influences the structures of rivers, lakes, streams and estuaries, since they are usually restricted to particular modes of life related to their food sources and reproductive requirements[8,9]. Like other animals, fish is also afflicted by endoand ectoparasites, especially protozoans and helminths causing heavy mortality[10]. Fish parasites and diseases constitute one of the most important problems confronting fish farmers today[11]. Pathological conditions resulting from parasites and diseases cause high magnitude of epidemics under crowded and other unnatural conditions[12]. The role of freshwater fish in transmitting parasites ARTICLE INFO ABSTRACT