An investigation on fingerling grass carp Ctenopharyngodos idella ectoparasites with the first occurrence of Tylodelphys clavata as a new locality record in northern Iran

Aquaculture in Iran has been developing quickly in recent years and includes the introduction of various new species such as Chinese carp (Ctenopharyngodon idella, Hypophthalmichthys molitrix, and Hypophthalmichthys nobilis), rainbow trout (Oncorhynchus mykiss) and stocks of common carp (Cyprinus carpio). The main aim of this study was to determine the external parasitic fauna of grass carp Ctenopharyngodon idella, from aquaculture facilities in northern Iran, alongside their prevalence level, intensity, and abundance. A total of 35 fingerlings of Grass carp with an average length of 10cm and an average weight of 7g was caught from a fish farm in Guilan province, northern Iran, and transported alive to the Parasitology laboratory in the autumn of the year 2019. Common procedures of Parasitology were performed for fish sampling. All specimens (prevalence of 100%) were infected with different parasite groups. Diplostomum spathaceum and Dactylogyrus lamellatus were respectively recovered from the eyes and gills of all fish, with a mean intensity of 14.8 and 8.6 each. Also, Ichthyophthirius multifiliis was observed at the highest level of 100% in the skin and gills, followed by Gyrodactylus sp. and Tylodelphys clavata were respectively detected in the skin and eyes of grass carp with the lowest prevalence value of 20% and intensity of 1, in common each. The record of Tylodelphis clavata in grass carp in the present study is considered the first report on the northern Iranian aquaculture system.