ABSTRACT
The increased daily demand for fish and its products in Nigeria has led to increased fish production by both public and private sectors. The determinants of pond water quality may include the sources of water (Borehole, taps, rivers) and the feed (poultry droppings or synthetic feed) used for fish farming as this could serve as an appropriate portal of diverse microbial species into the fish pond. This study was carried out to determine the physicochemical qualities and bacteriological burden of fish ponds source-water, fish-feeds, and effluents from fish farms in Benin City, Nigeria. Structured questionnaires were developed and shared to 36 fish farmers in Egor (10), IkpobaOkha (15) and Oredo (11) Local Government Areas in Benin City, Nigeria. On completion of the questionnaires, fish feed, effluents and source water samples were aseptically collected from these fish farms using sterile containers and transported to the laboratory immediately for analysis. The physicochemical parameters were evaluated for the source water and effluent samples using analytical methods. Standard microbiological methods were used for the analyses of the feed, source water and effluent for the evaluation of the heterotrophic and coliform bacteria. Isolated bacteria were further identified by molecular techniques. Phenotypic virulence properties such as were evaluated for the isolates. Antibiotic susceptibility of the isolates was carried out using Kirby-Bauer disc diffusion technique and the multiple antibiotic resistance index was evaluated. Data were analysed using Microsoft excel and PhyloT. Responses from questionnaires revealed that the source water used by fish farmers (100%) in Benin City were borehole water and 91.7% of fish farmers discharged effluents at least twice weekly into the surrounding environment. Physiochemical analyses of source water showed that the pH ranged from 6.01±0.23 - 7.11±0.19 while that of the effluent ranged from 6.13 ± 0.61 - 6.74 ± 0.19. The values for electrical conductivity ranged from 96.20 ± 58.91 - 293.00 ± 77.37 µS/cm for source water and 224.25 ± 77.35 - 315.83 ± 117.68 µS/cm for effluent xiii samples. Overall, the source water samples were found suitable for domestic use. The heterotrophic bacterial counts (log10 cfu/ml) ranged from 0.83 ± 1.17 - 1.88 ± 0.15 for source water, 3.34 ± 0.26 - 3.87 ± 0.47 for effluent samples and 2.50 ± 0.96 - 3.62 ± 0.12 for feed samples. Coliform counts on the other hand ranged from 1.49 ± 0.81 - 1.63 ± 0.63 for effluent, 0.13 ± 0.01 - 0.60 ± 0.24 for source water and 1.22 ± 0.61 - 1.75 ± 0.69 for feed samples. Identified bacterial isolates were species of Bacillus, Escherichia, Pseudomonas, Micrococcus, Staphylococcus, Salmonella, Chromobacterium and Proteus. Further characterization revealed the presence of Escherichia coli (18.28%), Proteus mirabilis (12.90%), Micrococcus luteus (4.30%), Salmonella enterica (7.53%), Chromobacterium violaceum (5.38%), Staphylococcus aureus (10.75%), and Bacillus pumilus (20.43%). Proteus mirabilis and Staphylococcus aureus were positive for virulence. The bacterial isolates were found to be susceptible to some of the antibiotics from different classes used in the study, such as meropenem, gentamicin, amoxicillin/clavulanic acid and ciprofloxacin, while resistance was observed most for sulfamethoxazole, erythromycin and tetracyclines. The isolates obtained from the effluents were found to be of public health importance. It was established that the fish feeds and source water accounts for about 30% of entire bacterial population in the effluents.
