Distribution of Aeromonas bacterial population in water, sediment and Nile tilapia in fish culture pond, Guder, Ethiopia

Abstract

Assessing heterotrophic bacterial population in water, sediment, and fish tissue assumes importance in predicting the quality of the fish and water quality in the culture system. The present study aimed to estimate the total heterotrophic bacterial population in water, sediment, and Nile tilapia (Oreochromis niloticus) cultured in an aquaculture farm at Guder Campus, Ambo University, Ethiopia. Water, sediment, and fish body tissue were collected from the fish rearing pond, and were estimated for total heterotrophic bacterial population. Various physico-chemical characteristics were recorded following standard methods. The level of bacterial population in water, sediment and fish tissue were done by following standard methods and expressed as colony-forming units (CFU) in water per milliliter (CFU ml^-1), sediment and fish tissues(CFU g^-1).The results revealed more bacterial population in sediment (3.43 x10⁶ to 5.54 x 10⁶ CFU g^-1) than in water (1.45x10⁶ to 4.0x10⁶ CFU ml^-1) and  fish tissues (1.06 ± 1.10x10⁴ to 1.74 ± 10.8x10⁴ CFU g^-1in gill filaments; 1.62 ± 11.2x10⁴ to 2.82 ± 13.0x10⁴ CFU g⁻¹ in intestine from; and 0.82 ± 5.9x10⁴ to 1.60 ± 12.1.6x10⁴ CFU g^-1; in kidney from 0.48 ± 5.0 to 0.77 ± 4.1x10⁴ CFU g^-1. in skin). Among fish tissues; the heterotrophic bacterial population was more in the intestine than other organs of Oreochromis niloticus. In conclusion, the total heterotrophic bacterial population was dominated in sediment than the other samples. The present study concludes that physicochemical characters of water influence the growth and survival of total heterotrophic bacterial population in fish pond. The development of stress due to changes in physicochemical characters of water, and rich nutrient load in pond soil facilitate the growth of pathogenic bacteria which infect the culture fish O. niloticus. The detrivore feeding habits of O. niloticus is responsible for more number of bacterial populations in intestine than in other organs.