Changes in Populations and Drift of Stream Invertebrates Following Lampricide Treatment

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Abstract
The effects of 3-trifluoromethyl-4-nitrophenol (TFM) treatment on invertebrate abundance, recolonization and drift rates were examined in 3 Great Lakes tributaries, having a wide range of water hardness. In the softwater streams only philopotamid caddisflies and lumbriculid worms were significantly reduced after the TFM treatment; their abundance in the untreated stream sections was unchanged. Treatment of the hardwater stream resulted in a dramatic mortality of leeches. Abundance of soft-bodied oligochaetes and Turbellaria were significantly reduced, while numbers of Simuliidae, Hydropsyche and Baetis increased 4 days after treatment. Daytime drift rates of the Annelida, Turbellaria, Amphipoda, Glossosomatidae and Tipulidae increased significantly during the lampricide treatment. Increased drift rates rather than mortality appears to be the major impact of the lampricide on invertebrate communities.