Effect of heterotrophic bacteria on the growth of tilapia (Oreochromis niloticus) cultivated in brackish water

Abstract

Tilapia is a commercial fish cultivated in both fresh water and seawater frequently attacked by pathogenic bacteria. Some bacteria have become probiotics and help overcome this problem. This study aimed to examined the effect of heterotrophic bacteria administration on survival rate and absolute weight growth of the fish, heterotrophic bacterial population growth and the water quality. The study used a factorial experimental design a x b, where a factor was the method of administering heterotrophic bacteria and b factor was the species of isolate used. Factor a consists of an introduction to fish via feed (a1) and via water test media (a2). Factor b consisted of b1 (diet without heterotrophic bacterial treatment), b2 (diet with heterotrophic bacterial isolate J), b3 (diet with heterotrophic bacterial isolate N), b4 (diet with heterotrophic bacterial combined isolates B, C, D, J (Vagococcus fluvialis), H, N; Bacillus cereus). The fishes were reared in a 60 l container. Administering via a feed of heterotrophic bacteria showed no significant effect to survival rate of tilapia. While administering via water showed a significant influence on the survival rate. Both administration methods caused a better absolute growth rate. However, administration of the bacteria did not affect the heterotrophic bacterial populations in the water.