Effects of CFT legumine rotenone on macroinvertebrates in East Fork Specimen Creek, Yellowstone National Park

Yellowstone National Park began a project in 2008 to restore westslope cutthroat trout (Oncorhynchus clarkii lewisi) to East Fork Specimen Creek.  As part of the restoration project, rotenone (CFT Legumine formulation) was used to remove nonnative and hybridized trout.  We evaluated the effects of these applications on benthic macroinvertebrate populations.  Macroinvertebrates were sampled before treatment, immediately following treatment, and 1 year post-treatment.  Pre-treatment macroinvertebrate communities were dominated by Ephemeroptera, Plecoptera, Trichoptera and chironomid taxa.  Preliminary analysis indicates that immediately following treatment, Ephemeroptera and Plecoptera taxa were reduced in abundance and richness, whereas Trichoptera and chironomids were minimally impacted.  One year post-treatment, Ephemeroptera and Plecoptera recovered in abundance and richness to pre-treatment levels.  To minimize impacts and maximize recolonization, we recommend applying the minimum dosage to eliminate fish and create colonization sources by breaking the drainage into multiple application phases.