Distribution of Aeromonas bacterial population in water, sediment and Nile tilapia infish culturepond, Guder, Ethiopia

Abstract

Assessing heterotrophic bacterial population in water, sediment and fish tissue assumes importance in predicting quality of the fish and water quality in 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.

Keywords

• bacterial population; nile tilapia; water quality; aeromonas bacterial