Seasonal differences in sensitivity of lampricide treatment in larval sea lamprey

Author / Creator

Schueller, Justin R

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Summary

Controlling larval sea (Petromyzon marinus) in Great Lake tributaries with the lampricide 4-nitro-3-(trifluoromethyl)phenol (TFM) via stream treatments is essential to reducing the number of spawni...

Controlling larval sea (Petromyzon marinus) in Great Lake tributaries with the lampricide 4-nitro-3-(trifluoromethyl)phenol (TFM) via stream treatments is essential to reducing the number of spawning-phase sea lamprey, an invasive species capable of collapsing the Great Lakes fisher. An important component of stream treatments is ensuring that the proper amount of TFM is applied to effectively control sea lamprey populations while minimizing the effects on non-target species. In this study, replicated streamside bioassays were conducted in May, July, and September 2021 on the Trout, Ocqueoc and Sucker Rivers to determine potential seasonal changes in sensitivity of lamprey to TFM. Larvae (≥ 60 mm) were collected with backpack electrofishers and then exposed to a continuous flow of TFM-treated stream water for 12 hours in parallel diluter systems. A suite of water chemistry and larval condition data were collected during these tests and used to model potential biotic and abiotic factors that influence seasonal differences in TFM sensitivity. The calculated minimum lethal concentrations to kill 99.9% of larval sea lamprey were 11-27% lower (May), 42-57% higher (July), and 43-73% higher (September) than predicted concentrations listed on the treatment charts utilized by sea lamprey control agents. Stream water temperature and larval glycogen appear strongly associated with seasonal sensitivity differences, suggesting that either parameter can be incorporated into the sea lamprey control program to conduct more efficient sea lamprey control, and reducing impacts to nontarget fish and other aquatic species.

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