Impact of the cestodeTriaenophorus nodulosuson the exoticLepomis gibbosusand the autochthonousPerca fluviatilis

Abstract

SUMMARYThe effects of plerocercoids of the cestodeTriaenophorus nodulosusinfecting the livers of native Eurasian perchPerca fluviatilisand non-native pumpkinseedLepomis gibbosuswas investigated in 17 sites along the Moselle watershed. With a single exception, infected individuals were not observed in the main channel whether or not northern pikeEsox lucius, a final host, was present. In ponds where the pike was present, the prevalence ofT. nodulosusaveraged 86% in Eurasian perch and 15% in pumpkinseed. The parasite was not present at all in ponds when pike were absent. Parasite load, hepatosomatic index (HSI), gonadosomatic index (GSI) and body condition index (CI) were compared between hosts in one site where parasite prevalence and fish abundance was highest. HSI in infected perch was significantly higher than in uninfected perch, whereas no differences in HSI were detected between infected and uninfected pumpkinseed. While perch were more frequently infected and had a greater average parasite load than pumpkinseed, there were no significant differences in either indicator between the two species. Furthermore, no significant differences in GSI or CI were observed between infected and uninfected fish in either species, by either gender or maturity stage. We hypothesize that pumpkinseed is more resistant to the parasite or less likely to feed upon infected copepods than perch.