Distribution and Persistence of the Lampricide Bayer 73 Following a Control Application

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Abstract
Bayer 73 (2-aminoethanol salt of 2′,5-dichloro-4′-nitrosalicylanilide) was applied to a 41-ha delta area of Seneca Lake, New York, to control the sea lamprey (Petromyzon marinus). Concentrations of Bayer 73 in lake water samples ranged from < 10 to 573 μg/L (ppb); concentrations peaked 2.5 h after application and were generally highest near the bottom and lowest at the surface, but exceeded 40 μg/L throughout the water column. All measured concentrations were 10 μg/L (limit of detection) or less within 96 h after application. Movement of the chemical out of the treatment area, as well as drift within the treatment area, was detected. Significant mortality of one species of caged fish occurred at the station with the highest Bayer 73 concentration 14 h after application. Fish tissue residues (< 10–858 ng/g) reflected water samples in concentration and distribution patterns; they were highest 14–24 h after application and then declined. In laboratory studies performed to determine the mechanisms affecting the decline in Bayer 73 concentrations, sediment processes — specifically adsorption — enhanced the decline.