Bacterial Flora in the Gastrointestine of Freshwater Fishes in the River

Abstract

The upper stream, midstream and downstream of the Tama River were chosen as stations 1, 2, and 3, and water quality and bacterial flora in the gastrointestinal tracts of fishes, water, sediment, aquatic insects and aquatic plants were bimonthly examined by using 10 different agar media under aerobic and anaerobic conditions. In the gastrointestinal contents of the freshwater fishes, facultative anaerobes, Enterobacteriaceae and Vibrio-Aeromonas group were always predominant but obligate anaerobes, Bacteroides type A and Bacteroides type B failed to be isolated from all fish samples. Vibrio-Aeromonas group, Bacteroides type A and Bacteroides type B which are known to be major components in the gastrointestinal tracts of cultured freshwater fishes; these were isolated from water, sediment and aquatic plants, so the bacteria in the gastrointestine of fishes in the natural waters are suspected to originate from the environment. In the water and sediment, log number of total viable counts was found to correlate with concentrations of COD. The relationship between vaible counts in each bacterial components and total viable counts in each habitat was discussed using the regression equation. © 1983, IEEE. All rights reserved.