Growth and behavioral effects of the lampricide TFM on non-target fish species

Although the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) has been used for over 60 years to control sea lamprey Petromyzon marinus in the Laurentian Great Lakes, its potential non-lethal impacts on non-target species have not been fully evaluated. We exposed juveniles of two species of fish (lake sturgeon Acipenser fulvescens and rainbow trout Oncorhynchus mykiss) and one adult fish species (fathead minnows Pimephales promelas) to various concentrations of TFM (0.25-7.5 mg/L) in three sets of experiments examining TFM effects on growth, avoidance of TFM treated water, and predation susceptibility. Lake sturgeon and rainbow trout were monitored for two weeks after a 12 hour exposure to TFM to observe differences in instantaneous growth among four treatment levels (0, 2.5, 5, and 7.5 mg/L TFM). Growth rates did not differ significantly among control and treated fish of either species. Next, potential avoidance of TFM by rainbow trout was evaluated in a test tank where half the water was contaminated with TFM (0, 0.25, or 2.5 mg/L). No avoidance behavior was observed as rainbow trout spent equal amounts of time in TFM and control water. Finally, fathead minnows were exposed at three different concentrations of TFM (0, 2.5, and 7.5 mg/L) and placed in mesocosms with a non-exposed largemouth bass Micropterus salmoides predator. Two separate trials were performed, both with no significant differences due to treatments. In summary, results indicate that for the conditions tested, TFM has no detectable sub-lethal effects on growth, avoidance behavior, or predation mortality on the fish species tested.