Forty years of fluctuation in the occurrence of two various metazoan parasites: Contracaecum multipapillatum (Nematoda) and Digenean metacercaria N1 in warm water fish culture in the Israeli farms

We present field observation results from October 2019 to February 2021 in Israeli fish farms. Surprisingly, two metazoan parasites, the larvae of Contracaecum multipapillatum and unidentified metacercaria N1, which disappeared from Israeli fish farming 30 years ago, were commonly found in the current study. The reappearance of these two helminths is likely related to changes in the management policy related to new regulations regarding bird-of-prey species. It means that farmers could have prevented parasitic infections by keeping away piscivorous birds from their fish ponds and by treating these ponds with appropriate compounds against the affected invertebrates.