Dissipation of Niclosamide Downstream from Granular Bayer Application Plots in Lotic Environments

Science Center Objects

Niclosamide (2-amino ethanol salt of 5-chloro-N-[2-chloro-4-nitrophenyl]-2-hydroxybenzamide, NIC) is the active ingredient in the lampricide Bayluscide®. Bayluscide® 70% wettable powder is typically used in combination with TFM to reduce the amount of TFM required for an effective treatment.  The 3.2% granular formulation of Bayluscide® is normally used alone to assess larval sea lamprey (Petromyzon marinus) populations or in conjunction with TFM or the combination of TFM and Bayluscide® wettable powder to treat areas infested with ammocoetes that are not effectively treated with liquid formulations of lampricides.

During stream treatments using Bayluscide® 70% wettable powder, the wettable powder is applied uniformly throughout the water column at a concentration proportional to 0.5 – 1% of the TFM concentration. The lampricide concentrations are maintained at ≤1.5 times the stream minimum lethal concentration for ammocoetes (Johnson and Weisser 1996) and below the LC25 of the most sensitive non-target species for a nine hour period. Typical NIC treatment concentrations are between 25 to 35 ppb. The fate of NIC residues in lotic waters following TFM and Bayluscide® wettable powder treatments has been investigated (Dawson 1998).
The fate of Granular Bayluscide® (gB) in lotic environments is not well characterized and there are concerns that toxic concentrations of NIC may move downstream from treatment plots and harm sensitive species.  Granular Bayluscide® is normally applied at the rate of 0.0175kg/m2 over or under the surface of the water. The granules sink to the sediment water interface were the NIC is released. The accumulation/dissipation of NIC in the sediment and water column downstream from gB applications has not been studied.


The objective of this study is to determine the concentration over time of NIC in sediment and water downstream from plots treated with gB in accordance with Sea Lamprey Control assessment procedures.

Sea lamprey Transformer, Petromyzon marinus
(Credit: Sue Schleis, USGS, UMESC. Public domain.)