Microbes for healthy fish in recirculation systems

In this project scientists are studying the microbes in the water of a recirculation system, together with the fish and the bio-filter in the system.

They want to know to what extent the design of an aquaculture system influences the composition of the microbe community, and what the effects of daily management are. In addition, they are studying whether the microbial composition has an effect on the health of farmed fish. 

Fish farmers keep a close eye on the chemical composition of the water in recirculation systems, but have no understanding of the composition of the microbial community in the water. Researchers believe, however, that this can influence fish health. Unnoticed shifts in composition from safe to unsafe bacteria can affect fish growth. The growth of fish in recirculation systems sometimes decreases, apparently inexplicably, after a number of years, whereas there have been no apparent changes in water quality.  

In this project scientists are studying the microbial community in the water, the fish (digestive tract) and the bio-filter to find out how its composition affects the health of the fish, in this case turbot. For the study they are using two very different types of recirculation systems used in turbot aquaculture. They are also looking at the effect of a change in feed on the microbial community. If more plant-based feed is used – desirable because of the shortage of animal protein sources – does this change the composition of microbes in the water and in the fish? And if so, does this affect the health of the fish?

Preliminary results have shown that there is a big difference between the bacterial composition in the two recirculation systems and in the activity of the immune system of the fish. The long-term aim is to be able to manage the microbial composition in an aquaculture system so that it is made up largely of beneficial microbes.