Infection of American Eels,Anguilla rostrata,by an Introduced Nematode Parasite,Anguillicola crassus,in North Carolina

Abstract

Recent studies have documented the occurrence of the nonindigenous swim bladder nematode parasite (Anguillicola crassus) in American eels (Anguilla rostrata) from Chesapeake Bay and Hudson River drainages. The parasite was originally discovered in a single American eel captured in Winyah Bay, South Carolina, in 1995. We examined eels from all major coastal rivers in North Carolina and recorded prevalence and mean intensity of infection. A total of 1111 eels were captured. Overall 52% were infected (prevalence ranged from 26–100% among rivers), and there were 1–53 nematodes per infected individual (mean intensity = 3.9). The condition of infected eels was not significantly different from that of uninfected eels; however, we found a significant positive relationship between mean intensity of infection and eel size. The infection rate of North Carolina eels was substantially higher than that reported in Chesapeake (10–29%) and Hudson River (0–12%) collections. The high infection rates we observed could be related to increased warm water periods in southern rivers or the fact that this exotic may have been introduced earlier in southern rivers than in northern ones.