Abstract.-Benthic fauna in the Betsie, Baldwin, and Green rivers, and both benthos and trout in the Sturgeon River, were studied for effects of lampricide treatments with 3-trifluormethyl-4-nitrophenol (TFM).
Sensitive species of benthos were reduced in the treated area of the Baldwin River and there was some evidence of reduction (although not significant) in the Green and Sturgeon rivers. However, Betsie River showed no effect of TFM 4 years after treatment. The Betsie River was resampled on August 9-10, 1983, just 3 days following TFM treatment. Dead lamprey ammocoetes were evident throughout the treated area, however, numbers of mayfly nymphs were not diminished. No differences in the trout population of the Sturgeon River were evident.