The protozoan parasite identified as Ichthyophthirius multifiliis Fouquet (1876) was first time noticed on snow trout (Asala) fry (Schizothorax richardsonii) reared in Godawari Fish Farm. The parasitism of I. multifiliis to Asla fish is a new occurrence in Nepal. Site of occurrence of I. multifiliis was observed in wet smear of skin, fin and gills scraping as well as in the underlying musculature of skin in histological studies. Diameter of isolated organisms I. multifiliis was measured ranges from 0.0505-1.1666 mm under microscope. The mean prevalence of I. multifiliis to Asala fry during rainy season (June 2007) estimated was 64.1 percent. The daily mortality rate of Asala fry, observed for nine days, due to I. multifiliis infestation ranged between 0.2 to 12.6 percent.

The protozoan parasite identified as Ichthyophthirius multifiliis Fouquet (1876) was first time noticed on snow trout (Asala) fry (Schizothorax richardsonii) reared in Godawari Fish Farm. The parasitism of I. multifiliis to Asla fish is a new occurrence in Nepal. Site of occurrence of I. multifiliis was observed in wet smear of skin, fin and gills scraping as well as in the underlying musculature of skin in histological studies. Diameter of isolated organisms I. multifiliis was measured ranges from 0.0505-1.1666 mm under microscope. The mean prevalence of I. multifiliis to Asala fry during rainy season (June 2007) estimated was 64.1 percent. The daily mortality rate of Asala fry, observed for nine days, due to I. multifiliis infestation ranged between 0.2 to 12.6 percent.