Saprolegnia infection and clinical findings in trout farms (Oncorhynchus mykiss). Technical note

• Filiz Özcan Dicle University, Veterinary Faculty, Fisheries and Fisheries Diseases Department. Diyarbakır, Türkiye.

DOI: https://doi.org/10.52973/rcfcv-e34469

Keywords: Saprolegnia spp., fungal diseases, Oncorhynchus mykiss

Abstract

The spread of Saprolegnia spp. can increase mortality rates in fish farms, the surrounding environment and natural populations; therefore, detailed surveys to track the spread of pathogenic Saprolegnia and their distribution from fish farms to the natural environment are critical and should be conducted regularly. In this study, Saprolegnia spp. were detected in fish samples collected from rainbow trout (Oncorhynchus mykiss Walbaum, 1792) farms in the Southeast Anatolian region. 40 trout farms in different provinces of the region were visited and 1000 samples were examined. 25 fish with an average live weight of 100–150 g were collected from each farm and the clinical picture was established after macroscopic examination of the fish samples in the laboratory. In order to detect and identify Saprolegnia growth in the culture environment, the fungus was grown by seeding on Anacker–Ordal (AO) 18°C agar for 5–7 days. As a result of the research, erosion, ulcer formation, increased mucus and fungus (Saprolegnia spp.) were detected in 798 skin samples. Anaemia in the gills, anaemia, hyperemia, oedema in the secondary lamellae and fungus (Saprolegnia spp.) were found in 341 samples. As a result, Saprolegnia spp. was found in farms located in this region. It has been established that in order to protect themselves from this infection, farms in the region must take care not to damage the fish bodies, remove dead and sick fish, not leave excess feed, avoid mechanical damage, pay attention to the deterioration of the mucoid layer, minimise stress factors by avoiding excessive stocking.

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