ABSTRACT
Parasites have a wide range of distribution in all groups of animals. They are more abundant than free-living animals, and may be found in every phylum of animal from protistan to chordates. A large number and diversity of animal species are capable of patrasitising fish, ranging from microscopic protozoans to easily visible crustaceans and annelids. Most of the fishes, either wild or cultured, are infected with parasites. They not only serve as the host to different parasites, but also serve as carriers of many larval parasitic forms that mature and cause serious diseases in many vertebrates, including man. Parasites exhibit marvelous strategies for adaptation to their hosts. Many parasite species are host-specific to some extent and are capable of infecting one or only a limited number of host species. Individual parasite species may also have widely differing effects on different host species (Roberts 2012). Some of them are parasitic in the external surface of fish; others are parasitic in the internal organs. They can infect fishes in different
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
