Current research on the environmental impact of Neoergasilus japonicus in the Great Lakes is inadequate to support proper assessment. Realized:
Neoergasilus japonicus can cause infected fish to hemorrhage at the attachment site.
In Saginaw Bay, Lake Huron, N. japonicus has most commonly been found infecting Pumpkinseed sunfish (Lepomis gibbosus), followed in frequency by Yellow perch (Perca flavescens), Rock bass (Ambloplites rupestris), Bluegill (L. macrochirus), Carp (Cyprinus carpio), Channel catfish (Ictalurus punctatus), Goldfish (Carassius auratus), Green sunfish (L. cyanellus), Smallmouth bass (Micropterus dolomieu), Largemouth bass (M. salmoides), and Fathead minnow (Pimephales promelas) (Hudson and Bowen 2002). In 2006, eight new hosts of N. japonicus were discovered in Saginaw Bay, including Bluntnose minnow (P. notatus), Common shiner (Luxilus cornutus), Emerald shiner (Notropis atherinoides), Golden shiner (Notemigonus crysoleucus), Quillback (Carpoides cyprinus), Sand shiner (Notropis stramineus), Spotfin shiner (Cyprinella spiloptera), and Spottail shiner (N. hudsonius) (Hudson et al. 2011).
Potential:
Neoergasilus japonicus could disperse outside of known locations and and has the potential to do so relatively quickly. In 20 years, it probably moved across Europe, where it has been introduced to such countries as the U.K., Finland, France, and Hungary. It is widely distributed and often associated with aquaculture. Within the Palearctic region, fish hosts are all cyprinids and percids. One of these is the Rudd (Scardinius erythrophthalmus), which has been introduced to and is established in Lake Ontario. N. japonicus is not limited to cyprinids and percids within North America; infection of centrarchids and ictalurids has also been reported (Abdelhalim et al. 1993, Hayden and Rogers 1998, Hudson and Bowen 2002, Jansson and Karppinen 1988, Knopf and Hoelker 2005, Lescher-Moutoue 1979, Mugridge et al. 1982, Ponyi and Molnar 1969, Tuuha et al. 1992). It was discovered colonizing multiple threatened cichlids in Mexico (Suárez-Morales et al. 2010).
There is little or no evidence to support that Neoergasilus japonicus has significant socio-economic impacts in the Great Lakes.
Potential:
Neoergasilus japonicus has invaded aquaculture ponds outside of the Great Lakes and has demonstrated the ability to infect many types of farm-raised fish (Hayden and Rogers 1998). The impact of these invasions is unknown.
There is little or no evidence to support that Neoergasilus japonicus has significant beneficial effects in the Great Lakes.