Identification of important pathogens in European perch (Perca fluviatilis) culture in recirculating aquaculture systems

Abstract

With the development of recirculating aquaculture systems (RAS), fish species, like European perch (Perca fluviatilis), can be produced efficiently. The lack of experience in the cultivation and emerging pathogens of this species often lead to high mortality during the production cycle. In this study, we evaluated diagnostic submissions of European perch from a warm water RAS analyzed at the Centre for Fish and Wildlife Health, University of Bern, in the years 2017 and 2018. The aim of this study was to identify important pathogens for this species to provide a base for future prophylactic and treatment concepts. The results demonstrated that bacterial infections were some of the most important issues in perch health, with Aeromonas sp. as one of the most commonly isolated. In histology, liver and muscle alterations with unclear cause and oomycete infections were frequently detected. Parasites and viral diseases were less prevalent. However, consequences of viral infections, like Perch rhabdovirus, would be detrimental for an RAS. This study shows the importance of a proper quarantine and the need for a protocol to reduce stress, as this is a major predisposing factor for disease outbreaks in European perch.