SUMMARY
Seasonal variation and site specificity of external parasites in gold fish (Carassius auratus) and koi carp (Cyprinus carpio) cultured at Rambadagalle fish breeding and training center were estimated during wet (February-July) and dry (August-November) seasons in 2013. According to the proportion of the total harvest, samples of 30 gold fish and 50 koi carps in same cohort were collected from two separated harvesting ponds. Their gills, skin scrape and fins were examined in the laboratory for ectoparasites, and the percentage prevalence of parasites at each site of two fish species during two seasons were calculated and compared statistically.Ten external parasite species (Trichodina sp., Apiosoma sp., Tripartiella sp., Chilodonella sp., Ichthyobodo necator, Gyrodactylus sp., Dactylogyrus sp., Centrocestus sp., Posthodiplostomum cuticola, Argulus sp.) were recorded from both fish species during two seasons. Posthodiplostomum cuticola and Chilodonella sp. were not recorded from koi carp while Argulus sp. was not detected from gold fish. Koi carps were highly parasitized during dry season while it was wet season for gold fish. During two seasons, for both fish species, percentage prevalence of Trichodina sp. (skin: ranged from 58%-100%, fins: 12% -97%) and Apiosoma sp. (skin: ranged from koi 28% - 100%, fins: 12% -82%) were high in skin and fins. In contrast, during two seasons, for both fish species high percentage prevalence of Dactylogyrus sp. (ranged from 37%-54%) and Centrocestus sp. (ranged from 62%-90%) were recorded from gills. For each fish species, total number of parasites infected in skin, fins and gills were significantly different (p<0.05) between two seasons.