On the occurrence of parasite, Lernaea cyprinacea from common carp, Cyprinus carpio farmed in ponds and rice fields

Lernaea cyprinacea and occurrence of Lernaeasis in farmed and wild warm water fishes is a major problem of aquaculture industry in Iran. The present study was conducted to compare the rate of L. cyprinacea infection between two separate populations of common carp, i.e., fish cultured in ponds and sampled from rice fields. To this end, fish sampling was done during 3 months in summer. After fish sampling, fish were transferred to lab for parasite study. Parasite incidence percent and density were calculated for two population carps. According to obtained results, the parasite incidence percent and density were significantly higher in fish samples taken from fish ponds than in those from rice fields (P < 0.05). In fact, fish from rice fields were more healthy compared to fish from monoculture ponds. In conclusion, our results show that the polyculture of carp with rice can control Lernaea infection. These results may be in relation to the controlling effects of used pesticides in particular diazinon in rice field on this parasite.