Revealing the first records of endoparasitic interactions in the non-native fish Moenkhausia costae within a reservoir in Northeastern Brazil.

Parasites are an important part of ecosystems, but are frequently ignored in studies on major anthropogenic impacts on aquatic environments. Biological invasions are responsible for biodiversity loss, and are one of the possible consequences of water transfer projects. In addition, there is a possibility that the non-native species brings, at least in part, its parasite fauna to the invaded area, or acquire new parasites in the new environment. Here, we investigated the endoparasites of a non-native fish species that was recently recorded in the upper Paraíba River basin, Northeastern Brazil, after a major water transfer project. Fifty specimens of Moenkhausia costae were collected from the Poções reservoir, Monteiro municipality, Paraíba State. Forty-two hosts were parasitized (84%), and 179 parasite specimens were collected. The endoparasite community was composed of six species of nematodes. There was no significant correlation between parasitism and the size of the hosts, nor the host's condition factor. Although the size of parasitized and non-parasitized fish did not differ, the relative condition factor was significantly higher for parasitized fish. Future studies should investigate which parasites were introduced with M. costae, and which ones were part of the invaded environment.