Relationship between condition factor and external parasite density of gold fish (carassius auratus (linnaeus, 1758)) and koi carp (cyprinus carpio (linnaeus, 1758)) during dry and wet seasons

Comparative study on relationship between condition factor and parasite density of gold fish (Carassius auratus) and koi carp (Cyprinus carpio) was carried out during wet and dry seasons. The study was conducted at the Rambadagalle Ornamental Fish Breeding and Training Center in Sri Lanka. A sample of 30 gold fishes and 50 koi carps in the same cohort were collected from two separated harvesting ponds. Standard length and weight were recorded and condition factor was estimated for each individual. Their gills, fins and skin were observed for external parasites. Among the recorded parasites, abundance of Tricodina sp. was high in gold fish during both seasons. Tricodina sp. was the most abundant parasite during the wet season in koi carp while it was Apiosoma sp. in the dry season. Correlation co-efficient was determined to investigate the strength of the relationship between condition factor and the total number of parasites. There was no significant correlation was observed between two factors for gold fish during two seasons (wet season= -0.287, dry season r = -0.109, P>0.05). A weak negative relationship was observed between condition factor and the number of parasites infected the koi carp during the dry season (r=-0.304, P= 0.032) but no significant correlation was observed between two factors during the wet season (r= 0.08, P= 0.580). Information emerged from this study could be taken into consideration when implementing health management practices in ornamental fish culturing programs.