Microbial Contamination of Nile Tilapia (Oreochromis Niloticus) and African Catfish (Clarias Gariepinus) Fingerlings Reared in Hatchery Tanks at Sagana, Jambo, and Mwea Fish Farms
Njagi, Isaac G
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In Kenya, aquaculture continues to expand as a source of food production and livelihood in all the counties. Mortality of Nile Tilapia and African Catfish fingerlings constitute the biggest loss in extensive and intensive fish farms. The main objective of this stud y was to determine contamination by bacteria and fungi in Nile Tilapia and African Catfish fingerlings . The study was carried out from March 2014 to July 2014 in fish farms with different water sources, hatchery systems and feed sources. These were; Jambo fish farm in Kiambu County which utilizes borehole water and has a recirculation aquaculture system also known as (RAS).Sagana and Mwea fish farms in Kirinyaga County. Four weeks old and weighing 5 7 g, Nile Tilapia ( Oleochromis niloticus ) and African Catf ish ( Clarias gariepinus ) 60 each in number were stocked as follows; in every hatchery tank 10 fingerlings of each species regardless of sex. Data obtained from samples was analyzed using descriptive statistics . Fish fingerlings samples and fish feeds were collected from three fish farms and taken to the Laboratory. The bacterial load of the samples was determined using the pour plate method. Identification and characterization of various isolates were based on gram staining technique, biochemical tests and subculture on selective media . Fungi were isolated on SDA agar, Macroscopy of hyphae and mycelium, microscopic identification of subcultured fungal isolates using LCBS stain and Mycology charts . The mean of bacteria isolated in the two fish species from th ree farms per cfu/mL was as follows: African Catfish had 9.00 ±3.85a, 27.752.85a and 21.67±4.82a for the Bacillus spp, Escherichia spp and Salmonella spp, respectivelly while Nile Tilapia had 8.58±3.68a, 25.25±3.54a and 22.83±4.95a, for the Bacillus spp, Es cherichia spp and Salmonella spp, respectivelly. Penicillium spp 33.1±2.5 cfu/g and Rhizopus spp 27.6±2.8 cfu/g occurred less frequently. There was a significant variation (p = 0.015) in the means of bacteria contaminants isolated in Sagana fish farm from N ile Tilapia and African Catfish species. Escherichia spp in the skin did not vary significantly (P= 0.0684) between the fish species, however African catfish skin had the highest 27.7± 2.8 Escherichia spp contamination. There was also significant (p< 0.0001) variation in Bacillus spp contamination in fingerlings skins from different farms. The occurrence of Klebsiella species 22.0±4.7 cfu/ml , Salmonella species 22 80±4.9 cfu/ml , Streptococcus spp 25.0±5 .4 cfu/ml while Vibrio spp had a mean of 2 0.0±3.6 cfu/m l There was no significant (P= 0.4857) interaction between fish species and farm in determining the Klebsiella spp in fish skin. Formulated feeds were more contaminated (25.58) than commercial feeds (1.15) (Table 4.6). Formulated feeds had higher contamin ations attributable to high moi sture, poor storage facilities, h andling and preparation methods For physiochemical parameters Salinity varied from 155.47±6.49 to 94.70 ±0.33 mg/L in Sagana and Mwea respectively with Mwea recording the least levels of salini ty . Water temperature in the morning ranged from 20.55±0.49 °C to 25.30±0.26 °C. I n the evening time, there was also a significant variation in the levels of temperature with Sagana recording the highest at 27.10±0.63, followed by Jambo 25.00±0.41 and Mwea h ad the lowest temperature of 20.15±0.43 Variations of salinity, temperature oxygen levels are among the parameters which determine the contamination for the two fish species among the three farms. It i s recommended that all farms supplying fingerlings appl y frequent assessment of water parameters, fish feeds and water analysis F ish farmers should be educated on best practices in aquaculture in order to prevent bacterial and fungal contamination.