Enriched environment keeps fish disease-free

A cooperative study conducted by the University of Jyväskylä and the Natural Resources Institute Finland (Luke) revealed that enriched rearing of juvenile fish significantly enhances the survival of fish from bacterial infection commonly seen in rearing conditions.

This may also improve the post-release survival of the fish after stocking into the wild, said a press release of the University of Jyväskylä and Luke.

The study findings have been published in the Journal of Applied Ecology.

The importance of aquaculture is increasing worldwide. Along with food production, rearing of endangered fish populations for supportive stocking has become important. In such actions, it is important that the behaviour and survival of introduced fish resembles to that of their natural conspecifics.

Traditional poor rearing environment offers favourable conditions for spread of parasites and diseases, which can significantly reduce the pre- and post-release survival of aquaculture fish. For enhancing the quality of stocked fish, enriched rearing method has been developed in Kainuu Fisheries Research Station of Luke in Paltamo.

In this method, structures are added to rearing tanks to increase habitat complexity and resemblance to natural conditions. Earlier, enriched rearing has also been shown to enhance survival of fish during disease epidemics in rearing conditions, but the underlying mechanisms have remained unclear.

New results about the effects of enriched rearing have now been achieved from collaborate study of the University of Jyväskylä and Luke. The study showed that enriched rearing enhanced the survival of Atlantic salmon (Salmo salar) and sea migrating brown trout (Salmo trutta) exposed to a common pathogenic fish bacterium, the Flavobacterium.

“Adding enrichments to rearing tanks significantly improved the survival of fish during natural disease outburst. However, there were minor differences between fish species and populations,” said PhD student Ville Räihä.