Physicochemical Parameters and Microbial Load of Cultured and Wild Catfish (Clarias gariepinus and Arius heudelotii) in Rivers State, Nigeria

Background: Aquaculture and wild fisheries are important for food security in Nigeria, but microbial contamination and water quality challenges threaten fish health and consumer safety. Methods: Physicochemical parameters (pH, dissolved oxygen, salinity, nitrate, temperature, and turbidity) and microbial loads were analyzed in cultured Clarias gariepinus (earthen pond, Aluu) and wild Arius heudelotii (New Calabar River). Microbial counts included total heterotrophic bacteria (THBC), fungi (TFC), coliforms (TCC), and Vibrio spp. (TVC). Standard APHA methods and ANOVA were applied. Results: Significant differences were observed in dissolved oxygen (pond: 8.11±0.15 mg/L vs. river: 4.93±0.18 mg/L, p<0.05) and salinity (river: 37.74±1.76 mg/L vs. pond: 17.95±0.15 mg/L, p<0.05). THBC in cultured fish (5.95–6.60 log CFU/g) exceeded wild fish (4.50–4.84 log CFU/g). Intestinal samples consistently had the highest microbial loads. Vibrio counts were significantly higher in pond water (3.50 log CFU/ml) than in river water (2.28 log CFU/ml). Conclusion: Physicochemical parameters strongly influence microbial colonization in catfish and aquatic environments. Cultured catfish carried higher microbial loads, with implications for aquaculture management and public health.