Isolation and Identification of Superficial Fungal Flora of Rainbow Trout Farms (Oncorhynchusmykiss) in Alborz Province, Iran

Opportunistic fungi are scattered in aquatic and soil environments. Predisposing factors such as density, transporting, handling, water pollution, manual feeding and other stressors play role for fungal infections outbreak, especially in sensitive specie like as rainbow trout.This fish is one of the popular species in Iran that is one of the major trout producers in the world. Because of that study of bacterial, fungal and parasitical flora in such facilities are highlighted. For this reason, Skin, fins and gills samples of 150 rainbow trouts (with healthy appearance) with 100.98± 5.48 g body weight from 15 facilities of Alborz province, in autumn and winter, 2016-2017 were collected. All the farms water resources were ground water (well). Samples were transferred to lab in sterile condition and under the laminar flow hood were cultured in Sabouraud Dextrose Agar with chloramphenicol, Corn Meal Agar and Glucose Peptone Agar. Cultured media were incubated in 23±1 ºC for at last 2 weeks. Grown fungal colonies were evaluated by their both macroscopic and microscopic methods.Out of surface samples, 103 fungal isolates were identified that 87 of that are molds belong to 11 genera besides 16 yeast isolates and out of gill samples, 82 fungal isolates were identified that 70 of that are molds belong to 10 genera and others were yeast isolates.In gills and skin, Aspergillus was the most frequent fungal genus and flavus was the most one among Aspergillus species. In order to the Chi square statistical test, there was no more significant correlation between identified fungal isolates in body surface and gills (P>0.05). But in most cases, the quantity of each isolated species was more in body surface than the gills.Fungi are present everywhere, and it is normal to be in water resources. Environmental pollutants (e.g. industrial, agricultural and municipal wastewaters) can provide productivity of water and entering the development of non- water molds. Diversity of fungal isolates is the indicator of poor water quality resulting low production, fungal infections increase as well as treatment and medication costs. Consumption of fungal spore-polluted fish food in facilities can be another way of entering of such fungal pollution.