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Abstract

Aquaculture management practices and water quality parameters influence bacterial occurrence in fish farms.This study aimed to identify the water quality parameters and aquaculture practices that cause bacterial occurrence in fish culture units in Machakos and Nyandarua counties.A cross-sectional study involved administering questionnaires to 46 randomly selected fish farmers and sampling water quality from fifteen selected fish farms from the two counties.The physico-chemical parameters collected and analyzed included; Temperature, turbidity, pH, organic matter content and dissolved oxygen levels in the fifteen selected farms.According to the findings, 45% of farmers in Nyandarua and 65% in Machakos use home-made feeds.All farmers in Nyandarua and 96% of farmers in Machakos use untreated pond water sources.Six heavy metals were detected from the water samples; Manganese, Iron, Calcium, Magnesium, Sodium and Potassium.Eight of the 15 sampled ponds had Manganese levels exceeding tolerable level of 0.05mg/L.Nine of the 15 ponds had Iron levels above the optimum of 0.3 mg/L.Fourteen of the 15 ponds had Magnesium levels below 75mg/L while 13 of the 15 ponds had Calcium levels below 75 mg/L.Only one of the 15 ponds had sodium levels below 1mg/L while four out of the 15 ponds had potassium levels below 1 mg/L.Bacteria genera isolated included Acinetobacter, Aeromonas, Enterococcus, Micrococcus, Pseudomonas, Bacillus, Flavobacterium, Enterobacter, Escherichia, Hafnia, Kurthia, Rhodococcus, Citrobacter, Exiguobacterium, Pseudarthrobacter and Lysinibacillus.The study reveals less compliance with biosecurity measures and good management practices for rearing fish in both counties which may result in high risk of heavy metal contamination.As a result, there is need for policy makers at national and county government levels to address these inadequacies through education and capacity building to enhance fish production.