Microbial load and diversity in the gastro-intestinal tract of cultured Nile tilapia (Oreochromis niloticus) and hybrid catfish (Clarias gariepinus ♀ x Heterobranchus bidorsalis ♂) in Ilorin Metropolis, Nigeria

Abstract

This study investigated microbial load and diversity of gastro-intestinal tract of the cultured Nile tilapia ( Oreochromis niloticus ) and hybrid catfish ( Clarias gariepinus ♀ x Heterobranchus bidorsalis ♂) in Ilorin metropolis, Nigeria. A set of apparently healthy Nile Tilapia and hybrid catfish were obtained from a fish farm in Ilorin metropolis. After dissecting the fish sample aseptically, the entire alimentary canals of the specimens were divided into foregut, midgut and hindgut. Then bacterial isolates were characterised, following standard operating procedures for gram reaction, morphology, motility, catalase and oxidase reactions, citrate utilization, coagulase production, starch hydrolysis, sugar fermentation, and eventual identification of the resultant colonies. The moulds were examined based on their micro-morphology as well as the colour and micro-morphology of their sporulating structures and conidia. The results of the study revealed that microbes were present in the entire gastro-intestinal tract of cultured hybrid catfish and Nile tilapia with highest microbial load found in the hindgut of the two fish species under study. Also, larger number of bacteria diversity indices were found in the hindgut of cultured Nile tilapia, while the hindgut of cultured clariid catfish had higher fungi diversity indices.