Water quality, bacterial load and hematological investigations of three over-wintering catfishes in Mymensingh District of Bangladesh

BACKGROUND: Studies were conducted to determine the water quality parameters, bacterial load in water and hematology of Pangasianodon hypophthalmus, Heteropneoustes fossilis and Ompok pabda reared in 15 over-wintering catfish ponds located at different upazila under Mymensingh district. METHODOLOGY: Participatory rural appraisal (PRA) technique tools such as personal interview, focus group discussion (FGD) and key informant interview with fish farmers were done to collect preliminary data. Fish and water samples were collected from catfish ponds and were analyzed in the Fish Disease Laboratory, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh, Bangladesh. The microbial loads of pond water (CFU/ mL) were determined by ten-fold serial dilution using Tryptone Soya Agar (TSA) after incubation at 25 °C for 48 h. Hematological analysis of blood samples were done to determine RBC, WBC, hemoglobin, blood glucose level and Mean Corpuscular Hemoglobin (MCH) of the over-wintered catfish. KEY FINDINGS: It was found that the water temperature, pH, dissolve oxygen, total alkalinity and ammonia ranged from 27 to 20.5°C, 8.2 to 7.0, 7 to 5 ppm, 190 to 120 ppm, 0.03 ppm, respectively during the study period. Among the 15 ponds, the highest and lowest temperature was recorded in P. hypophthalmus ponds. The highest alkalinity was observed in P. hypophthalmus ponds and minimum was found in O. pabda ponds. The ammonia concentration was more or less similar (0.03 ppm) in 15 ponds. Average bacterial load of rearing water was ranged from the highest 2.6 ± 1.60 ×105 CFU/ mL to lowest 2.3 ± 1.93 ×103 CFU/ mL in H. fossilis ponds. The study revealed maximum RBC, WBC contents and the highest glucose level in O. pabda and minimum in H. fossilis and P. hypophthalmus. However, MCH and hemoglobin levels were found higher in P. hypophthalmus and lower in O. pabda. CONCLUSION: The study revealed preliminary data regarding over-wintering farm condition, bacterial loads of over-winter water, hematology and water quality parameters of three over-wintering catfish which also indicated the unplanned management of over-wintering ponds that sometimes affects water quality and hematology of catfish. The findings may contribute for the proper health management of fish reared under over-wintering condition.