Infections of Gyrodactylus are reported at a Minnesota baitfish farm producing golden shiner (Notemigonus crysoleucas) in earthen ponds. Intensities reached approximately 100 parasites per fish, with no apparent sign of disease. Two species were present: Gyrodactylus crysoleucas Mizelle and Kritsky, 1967, was common (90% of the Gyrodactylus population), while an unidentified Gyrodactylus sp., morphologically resembling Gyrodactylus wellborni Nowlin, 1968, but not confirmed as such, was less so (10% of the Gyrodactylus population). We provide supplemental morphological and molecular diagnostic information on these understudied parasites. The 2 species of parasites are easily confused diagnostically with Gyrodactylus salmonis Yin and Sproston, 1948, and Gyrodactylus colemanensis Mizelle and Kritsky, 1967, from salmonid fishes in North America, but can be differentiated on the basis of differences in shape and size of the haptoral hard parts and provided 18S and ITS sequences. The case history is puzzling in that the farm has been self-contained for 25 years, operating through in-house production of brood stock, with no opportunity of acquiring parasites from local wild golden shiner. The study concludes that both G. crysoleucas and the Gyrodactylus sp. arrived with the original wild brood stock and have persisted unnoticed until now.