Abstract:The present study was conducted in three upazilla (Bagerhatsadar, Fakirhat and Rampaul) to investigate the shrimp diseases and culture strategies of Bagerhat district in 2012. Post larvae (PL-13/21) from hatchery and natural were used to stock in the study area. The highest mean stocking density was recorded in the ghers of Rampaul (16796±7729.69 PL/ha), where the maximum survival rate was also found (63.00±11.52 %). The highest dose of lime was recorded as 302.58±50.92 kg/ha at Bagerhat sadar; cowdung was recorded as 605.16±118.46 kg/ha at Fakirhat upazilla and urea was recorded as 29.02±5.84 kg/ha (Bagerhat sadar) respectively. The maximum doses of MP and TSP were recorded as 34.58±4.51 kg/ha at Bagerhat sadar and Fakirhat and 27.79±3.71 kg/ha at Bagerhat sadar respectively. No supplementary feed were fed to shrimp, in where culture dependent on natural foods. The highest shrimp production was found in Fakirhat upazila (667±307.05 kg/ha) and the lowest production was in Rampaul upazilla (497±268.97 kg/ha). Sudden change of p H , low dissolved o 2 levels, salinity variations, nutritional deficiency and other environmental changes causes yellow head viral disease (YHD), white spot syndrome viral (WSSV), vibriosis, fusarium and protozoan were recorded during the experimental period.

Effects of different chemotherapeutics were examined against experimentally infected stinging catfish Heteropneustes fossilis. Fish were collected from a fish market in Mymensingh, acclimatized for 7 days in laboratory condition from January to February, 2016 in aquaria at Fish Clinic of Bangladesh Agricultural University, Mymensingh, experimentally injured by using forceps and knife and waited seven days for the establishment of infection. Before starting chemotherapeutic trial, it was confirmed that the fish were infected with microorganisms by clinical diagnosis in laboratory condition. They showed hemorrhages and ulcerative lesions over the infected area. A total of 80 such experimentally infected stinging catfish having average body weight of 18 g were used for the experiment. Two chemotherapeutics: antibiotic, Eryvet (erythromycin thiocyanate INN, sulphadiazine (NaUSP) & trimithoprim BP) and antifungal, methylene blue were used in separate and combined treatment with three different doses of antibiotic. The same dose of methylene blue, 0.2 mg/l, was used for separate and combined treatment by antibiotic. Doses of antibiotic (Eryvet) were 0.8 g/10 kg body weight of fish, 1g/10 kg body weight of fish and 1.2 g/10 kg body weight of fish as lower dose, recommended dose and higher dose respectively. For combined treatment the above different doses of antibiotic and the same dose of antifungal were used. Water was exchanged regularly. The chemotherapeutic trial was conducted for 7 days and observation was continued for another 8 days to observe the effect of treatment. Combined treatment with the recommended dose of the antibiotic and methylene blue showed the best result where 90% fish were recovered. By the treatment with the higher dose of the antibiotic 70% fish were recovered. Antifungal treatment showed that 20% fish were recovered. All the fish in negative control aquarium died.

This study was intended to address, the effect of oxytetracycline, erythromycin, and streptomycin on the antimicrobial resistance of Aeromonas sp. isolated during the production process, from infected common carp (Cyprinous carpio). Antimicrobial resistance patterns were defined by determination of minimal inhibitory concentrations (MIC) of three antimicrobial drugs, and bacteria. Results indicated that In vitro bactericidal activity, oxytetracycline showed lowest number of bacterial colonies (1×10-4 c.f.u./ml) than erythromycin (3×10-4) and streptomycin (4.5×10-4) compared to the control (9×10-4). Oxytetracycline showed the highest maximum zone of inhibition (20 mm) than erythromycin (18 mm) and streptomycin (15 mm) in antibiotic susceptibility test. In infection inhibition assay, serum from oxytetracycline fed diets inhibited Aeromonas infection to common carp. The susceptibility of the fish fed antibiotics (50 µg/mg feed) and challenge with Aeromonas sp. (1×10-4) was examined for 30 days. There was high relative percent of survivility (RPS) in oxytetracycline was 73%. Very low RPS 63% and 47.37% was found in erythromycin and streptomycin against Aeromonas sp. infection. These results demonstrated that the oxytetracycline might be a potential for Aeromonas sp. infection to common carp (Cyprinous carpio).