Assessment of management practices and occurrence of mycobacterium marinum infection in selected milkfish (Chanos Chanos) farms in Zanzibar, Tanzania

M.SC. Dissertation

Milkfish farming in Zanzibar is at infancy stage, practiced at small-scale levels and faces a number of constraints including fish health problems. The purpose of this study was to assess the milkfish farming practices and possibilities for occurrence of Mycobacterium marinum infection in selected milkfish farms in Zanzibar, Tanzania. A questionnaire survey was administered to 24 milkfish farmers to acquire information on general management system, fish health and related problems. Pond physicochemical characteristics were assessed using standard procedures. Pond water (24), sediments (24) and fish (240) samples were collected for laboratory analysis ofw21 M. marinum using standard procedures. Most (92%) of farmers were smallholder with backyard ponds. About (91.7%) of the ponds were of earthen type adopted from salt pans and practiced polyculture (Chanos chanos + Mugil cephalus) technique. Fingerlings were obtained from the sea, some farmers did not feed their fish and there was no routine water exchange in ponds. Likewise, fish farmers were not aware about fish health related issues and fish mortalities were reported. Water temperature ranged between 29.3 οC to 37.1 οC varying significantly (P<0.05) between ponds. Dissolved oxygen ranged between 1.9 and 6.1 mg/l while the mean pH was 7.5 ± 0.5 and 8.2 ± 0.2. All sampled fish were apparently healthy. A total of 110 samples had bacterial growths on Lowenstein- Jensen media but only 12 (4.2%) were AFB positive. No any isolate was found to have DNA band size of 1030 bp for Mycobacteria which implied that they were not Mycobacterium. It is concluded that fish pond management practices was poor and farmers lack of knowledge on good management practices for optimal milkfish production. Health related problems exist in fish ponds but not mycobacteriosis. Education on fish diseases should be provided to farmers and researches on fish diseases including mycobacteriosis are recommended.