Hoplias malabaricus and Hoplerythrinus unitaeniatus are Erythrinidae family widely distributed in the Amazon River system of great value to both commercial and subsistence fishing for riverine populations. As such, the objective of the present study was to investigate the endoparasite communities of H. malabaricus and H. unitaeniatus of a tributary of the Amazon River in the north of Brazil. The endoparasite communities of H. unitaeniatus and H. malabaricus were taxonomically similar (85%) and consisted of Clinostomum marginatum, Contracaecum sp., Guyanema seriei seriei, Procamallanus (Spirocamallanus) inopinatus, Pseudoproleptus sp. and Gorytocephalus spectabilis, although the dominant endoparasite was C. marginatum, which was the most prevalent and abundant. All the specimens of both H. malabaricus and H. unitaeniatus were parasitized, with a total of 1237 helminths collected in the former host and 1151 helminths collected in the latter. Hoplerythrinus unitaeniatus possessed greater parasite species richness. Both hosts had an aggregate dispersion of parasites, and the abundance of C. marginatum, Contracaecum sp. and G. spectabilis correlated positively with the weight and length of the hosts. The condition factor was not affected by parasitism, but the abundance of C. marginatum and Contracaecum sp. increased when the condition factor of the hosts decreased. This is the first report of G. seriei seriei for H. malabaricus and Pseudoproleptus sp. for H. unitaeniatus.
