Diplostomum in pond-reared walleye Stizostedion vitreum—implications of a management strategy for control

Abstract

Severe outbreaks of the eye fluke, Diplostomum sp., in age 0+ walleye, Stizostedion vitreum, at the New York State Department of Environmental Conservation (NYSDEC) South Otselic State Fish Hatchery during the summers of 2000 and 2001 prompted a study of the prevalence of the metacercariae of this digenetic trematode in the walleye and cercariae in Stagnicola catascopium and Stagnicola elodes snails during the summer of 2002. During 2002, 2 fish out of the 195 examined had a single metacercaria in one eye each and two snails of 1670 examined shed two different types of cercariae that were of the order Strigeidida, which includes Diplostomum spp. A third cercariae of the xiphidiocercaria type was recognized in a total of 167 snails examined. Reasons for the marked decline in the presence of the eye fluke from summer of 2001 to summer of 2002, include the impact of management strategies to discourage the presence of fish eating birds as well as the life span of local snails, which appears not to exceed 2 years.