FISHERY TECHNOLOGY Research Note Prevalent Diseases among Freshwater Ornamental Fishes in Nagaon District, Assam Binod Kalita*, Krishna Kanta Tamuli, Sangipran Baishya and Omeo Kumar Dutta College of Fisheries, Assam Agricultural University, Raha - 782 103, India Received 16 June 2010; Revised 20 March 2012; Accepted 29 May 2012 * E-mail: cfsc_raha@rediffmail.com Disease is one of the limiting factors associated with ornamental fish trade. Office International des Epizootics (OIE) has detailed provisions for import or export of aquatic animals aimed at avoiding risk of disease transmittance (OIE, 1977). However, the ornamental fishes are not covered by these health codes and tropical ornamental fish trade operates without appropriate quarantine practices. Interna- tional ornamental fish trade often sustains economic losses, as a result of various infections soon after arrival in importing country or during transporta- tion (Jeong et al., 2002). The North Eastern Region is a hotspot of biodiversity, having 267 fish species of which 57% has ornamental potential (Sen, 2000). In view of the potential trade opportunities and government initiatives, many entrepreneurs are getting involved in ornamental fish trade in recent times. While bulk of the trade of exotic fishes is within the region, indigenous ones are exported through recognized traders in Kolkata (Kalita & Kalita, 2007). The objective of this investigation was to record disease incidences in captive culture of imported and locally collected potential ornamental fishes in Nagaon district of Assam. A total of 932 fishes of fifteen species were examined from fish shops, instructional unit of the College of Fisheries, Raha and collection sites of Kollong River at regular intervals of 25 to 30 days during the year 2006 - 07. Parasitic incidences noticed were further examined by scraping body surface mucus from areas of the pectoral fin, adjacent to dorsal fin, operculum, excised gills, lesions and intestine for proper identification under microscope. Use of fresh specimen facilitates visualization of motile parasite (Post, 1987; Southgate, 1994; Wildgoose, 1998). Others were preserved in 10% buffered formalin and 70% ethanol for identification using keys of Kabata (1985) and Cone (1995). For isolation of causative agent of bacterial diseases, selective media such as Rimler  Shotts (Shotts & Rimler, 1973) and Kings B Medium (King, 1964) were used in addition to other standard media viz; nutrient agar, tryptone soya agar (TSA) and brain heart infusion broth. Pure culture was obtained by repeated streaking and about 100 colonies were randomly taken in TSA (Himedia, India) slant as stock culture. To identify the bacteria to genus level, the scheme of Bain & Shewan (1968) and Le Chevallier et al. (1980) were pursued. Cultures exhibiting positive oxidase reac- tion, fermentative metabolism, motility and resis- tance to vibriostatic agent O/129 were considered to be Aeromonas sp. and subjected to biochemical scheme proposed by Popoff & Veron (1984) to ascertain the species. Identification of Pseudomonas to species level was done following the scheme of King (1964). Of the 932 fishes examined 26.5% was infested by 10 different diseases (Table 1). Four types of parasitic infections were due to one platyhelminth (Clinostomum sp.), two crustaceans (Argulus foliaceus and Lernea cyprinacea) and one sporozoan (Myxobolus sp.). The maximum prevalence (3.65%) was by Clinostomum sp., followed by A. foliaceus (3.43%) and least (0.64%) by Myxobolus sp. and Lernea cyprinacea. Two fungal diseases, Epizootic Ulcerative Syndrome (EUS) (5.69%) caused by Aphanomyces sp. and Saprolegnia sp. were recorded. The EUS infection was detected only in indigenous ornamental fishes. Fishery Technology 49 (2012) : 206 - 210 ' 2012 Society of Fisheries Technologists (India)