Cooperative Fish and Wildlife Research Units Program: Colorado
Education, Research and Technical Assistance for Managing Our Natural Resources

Windy Gap Reservoir (WGR), a 38 hectare impoundment on the Colorado River in Middle Park, Colorado, has been a major point source of production of triactinomyxon (TAM) actinospores of Myxobolus cerebralis (Mc) since the 1990s. Beginning in 2001, TAM production in WGR declined dramatically and remained low through June 2006. The decline was correlated with a change in oligochaete dominance from parasite susceptible strains of Tubifex tubifex (lineage III) to resistant strains (lineages I, V, VI). These results support the hypothesis that resistant T. tubifex lineage worms (I, V and VI) are acting as biofilters in WGR and may deactivate myxospores of M. cerebralis, thereby reducing ambient levels of TAM production.