Studies on the heterotrophic bacteria in the gastrointestinal tract of fishes. I. The intestinal microflora of carp Cyprinus carpio, grass carp Ctenopharyngodon idella and tilapia Sarotherodon niloticus.

Abstract

Microflora in the contents of intestinal tract of carp, grass carp and tilapia was investigated using 7 different agar media. The intestinal microflora varied with the species of fish. The predominant bacteria in the intestinal tract of carp were Aeromonas hydrophila, Bacteroides type A, Citrobacter freundii, Pseudomonas and Micrococcus. The intestinal microflora of grass carp mainly consisted of A. hydrophila and Bacteroides type A. The intestinal microflora of tilapia was mainly composed of Bacteroides type A, Bacteroides type B, Plesiomonas shigelloides and A. hydrophila. The ratio of the obligate anaerobes to the facultative anaerobes plus aerobes of carp, grass carp and tilapia was 0.05 to 0.95, 0 to 0.49 and 32.4 to 111.1, respectively. It is suggested that the predominance of obligate anaerobes in the intestine of tilapia was due to their long intestine.