**The title, authors, and abstract for this completion report are provided below. For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**
William D. Swink1 and Brian P. Neff2
1U.S. Geological Survey, Great Lakes Science Center, Hammond Bay Biolgoical Station, 11188 Ray Road, Millersburg, MI 49759
2U.S. Geological Survey, 6520 Mercantile Way, Lansing, MI 48917
Abstract
Areas of low-volume, focused groundwater inflow did not provide refuges where sea lamprey (Petromyzon marinus) larvae could survive exposure to the lampricides TFM and niclosamide during stream treatments. Areas of low-volume, focused groundwater inflow could be identified in summer only by measuring for differences in temperature between the stream substrate and stream water. Water samples were collected in four study areas during lampricide stream treatments in three streams in 2006 (Bear Creek, Michigan) and 2007 (Pigeon River, Michigan, and White River, Michigan). Groundwater samples were collected about 10 cm beneath the substrate using mini-piezometers (PushPoint samplers) and stream water samples were collected just above the substrate surface by uncapping 20-mL test tubes. Analysis of the water samples found no or only trace concentrations of lampricide in the groundwater at sites within areas of groundwater inflow. Higher concentrations of lampricide were found in water samples collected in the substrate at sites outside the areas of groundwater inflow. The volume of groundwater entering the stream was not sufficient to affect lampricide concentrations in stream water. The absence of lampricide in the groundwater samples show that areas of focused groundwater inflow could potentially allow sea lampreys to survive a stream treatment; however, post-treatment electrofishing surveys in the four study areas and in six additional study areas in Pigeon River found no surviving sea lamprey larvae at any site of focused groundwater inflow. Burrows of long-established sea lamprey larvae are lined with excreted mucous, and water for respiration is most likely drawn from the stream rather than the groundwater, allowing them full exposure to lampricide during a stream treatment. Further, the low volumes of groundwater emitted from these sites rapidly mixed with stream water containing lampricide, and did not attract free-swimming larvae from nearby areas to burrow into lampricide-free groundwater that was available. Although numerous, the small (6 to 60 m2) areas of focused groundwater inflow do not appear to allow appreciable survival of sea lamprey larvae during stream treatments, and probably do not warrant further investigation or concern by sea lamprey treatment personnel.