Fungal infections in salmonid stocks

Fungal infections represent an increasingly significant threat to salmonid aquaculture, particularly during egg incubation and early developmental stages. In Bavarian fish farming operations, outbreaks—primarily caused by Saprolegnia spp. and other opportunistic water molds—have increased markedly in both frequency and severity in recent years. This leads to substantial economic losses and also threatens the genetic diversity of locally adapted trout populations.

Despite their importance, the spectrum of pathogens in Bavaria remains insufficiently characterized, and routine diagnostics usually do not allow for precise identification at the species level. The aim of this pilot study is therefore to systematically assess the diversity and distribution of fungal pathogens in Bavarian salmonid stocks and to develop effective control strategies.

To this end, samples are collected from fish farms, fungal isolates are cultivated, and subsequently characterized using molecular biological methods. Based on these findings, specific PCR- and qPCR-based diagnostic methods are developed and validated to enable rapid and reliable identification of relevant pathogens.

In parallel, the antifungal efficacy of hypochlorous acid (HOCl) is investigated in both in vitro and in vivo experiments, including controlled treatments of salmonid eggs. Based on these results, practical standard operating procedures for application in aquaculture are developed.

The study provides a scientific foundation for improved diagnostics, targeted disease control, and sustainable production strategies in Bavarian aquaculture.

The project is co-funded by the European Union and supported by the Free State of Bavaria through the European Maritime, Fisheries and Aquaculture Fund 2023–2029 (EMFAF).