Tilapia is the third important finfish species group cultured worldwide in terms of production. The bio-floc culture system is a technology to manage the water quality and cultivation of beneficial microorganisms to support the cultured life. In this study, we report the impact and effect of water quality on bacteria diversity from bio-floc cultured Oreochromis spp . in Chini, Pahang. 30 tilapias from bio-floc farm in Chini, Pahang were randomly sampled monthly over an 8 -month culture period . The eye, brain and kidney were sampled for bacterial isolation, following identification of bacteria using biochemical test and commercial identification API kits. Water temperature, depth, pH, iron, sulfide, ammonia, nitrite, phosphate, and dissolved oxygen at each sampling site were also measured and recorded.
The results showed that Plesiomonas shigelloides is the most abundant bacteria species present in the fish sample with 20% followed by Sphingomonas paucimobilis with 18%. Other identified bacteria were Micrococcus spp. , Citrobacter freundii , Alcaligenes spp. , and Actinobacter baumannii with 8% for each bacterium. The lowest identified bacteria abundance were Staphylococcus hominis , Staphylococcus epidermidis , Kocuria varians , and Burkholderia pseudomallei with abundance percentage of 2% each bacterium (Figure1).
Multivariate analysis showed that ammonia was positively associated with the presence of high abundance bacteria Plesiomonas shigelloides, Alcaligenes spp., and Actinobacter baumannii . Meanwhile , iron and nitrite were strongly associated with Micrococcus spp. , and Citrobacter freundii (Figure 2) . Understanding the association between bacteria and their environment, especially water quality will strategize in prevention and diseases management caused by fish pathogens in the future.