Water Quality in Fish Farms: Influence of Biotic and Abiotic Factors and the Occurrence of Multidrug-Resistant Aeromonas spp.

Objective: To evaluate the water quality in fish farms located in the Recôncavo region of Bahia, considering biotic, abiotic, and microbiological parameters, in order to understand the environmental and sanitary conditions of these farming systems. Theoretical Framework: Water quality monitoring is essential for the sustainable management of aquaculture and is regulated in Brazil by CONAMA Resolution No. 357/2005, which establishes physical-chemical and biological limits for water intended for aquaculture. Phytoplankton is an important environmental indicator, while Aeromonas spp. stands out as an opportunistic pathogen associated with disease outbreaks in intensive farming systems and inadequate management. Method: Bi-weekly water and sediment samples were collected from September to November 2022 to assess temperature, pH, transparency, ammonia, nitrite, phytoplankton, thermotolerant coliforms, E. coli, and Aeromonas spp. Isolated Aeromonas strains were subjected to antimicrobial susceptibility testing and virulence factor assessment. Results and Discussion: Temperature, nitrite, and pH values remained within recommended limits. At point P2, 70% of the samples showed transparency greater than 70 cm, while at point P3, ammonia concentrations above 0.1 mg/L were observed, associated with a predominance of cyanobacteria. Thermotolerant coliforms exceeded legal limits at points P2 and P3, and E. coli was detected in all evaluated fish farms. Aeromonas spp. was isolated from 8% of water samples and 30% of sediment samples, with strains exhibiting virulence enzyme production and multidrug-resistance antimicrobial profiles. Research Implications: The results provide insights for improving sanitary and environmental management in fish farms, contributing to disease prevention, reducing public health risks, and promoting aquaculture sustainability. Originality/Value: The study integrates analyses of physicochemical, biological, and microbiological parameters, including opportunistic pathogens and antimicrobial resistance, across family and commercial fish farms, providing relevant information for environmental monitoring, the adoption of good management practices, and food safety.