Gyrodactylus use their sharp anchors to attach themselves to their host (40X magnification). Photo by: Eric Leis

Embryos devloping inside of the adult gyrodactylus. Photo by: Eric Leis

A closeup of the developing Gyrodactylus embryos (40X magnification). Photo by: Eric Leis

Staff from the La Crosse Fish Health Center, Iron River National Fish Hatchery and the Upper Midwest Environmental Sciences Center (USGS) recently completed a study determining the effectiveness of hydrogen peroxide in controlling Gyrodactylus outbreaks in brook trout.  Gyrodactylids are small ectoparasites which can cause serious problems if they are found in high numbers on the skin and gills of fish.  These parasites are unique because they are viviparous, or live bearing, meaning that a developing embryo can be observed inside the adult.   Over the course of the study, brook trout were separated into treatment groups and mucus scrapes were observed for the presence of parasites.  The parasites were counted and identified.  Species identification involved measuring and observing the shape of different sclerotized parts of the parasite.  The results of this study will be published in a fisheries-related journal.