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EVALUATION OF EMERGENCE TIMES OF LARVAL SEA LAMPREYS (Petromyzon marinus) EXPOSED TO BAYLUSCIDE 3.2% GRANULAR SEA LAMPREY LARVICIDE UNDER VARYING WATER TEMPERATURES
Michael A. Boogaard1; Jean V. Adams, PhD2; Terrance D. Hubert, PhD1; Nicholas J. Schloesser1
1 U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road. La Crosse, Wisconsin 54603
3U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road. Ann Arbor, MI 48105
We conducted a series of dissolution trials of 3.2% Bayluscide® Granular Sea Lamprey Larvicide at selected water temperatures to evaluate if release of the chemical from the granular formulation was influenced by water temperature. Trials were conducted at 5, 12, and 21 °C. Average release times were 3.67, 3.87, and 3.38 min for the 5, 12, and 21 °C, respectively. There was no evidence that water temperature had any effect on Bayluscide® granule release times based on a simple linear regression. We also conducted a series of larval sea lamprey emergence trials at selected water temperatures of 6, 8, 10, 12, 16, and 21 °C to evaluate the influence of water temperature on larval emergence after application of the granular Bayluscide® formulation. The granular formulation of Bayluscide® is used to assess larval sea lamprey populations in areas of a stream where electrofishing is impractical. Current protocols call for monitoring for larval emergence for 1 hour after the granular formulation is applied. Numbers of larvae collected over the 1 hour period are then used to estimate densities for stream treatment ranking purposes. Concerns have been expressed that the 1 hour monitoring time is insufficient at lower water temperatures. Overall, the emergence data fell into two groups, data from trials < 12 °C and from those >12 °C. After 1 hour fewer than 30% of larvae emerged at temperatures < 12 °C, but more than 77% emerged at temperatures > 12 °C. Based on the data, the maximum temperature that would trigger a longer monitoring duration would be 12 °C. In order to maintain the same emergence efficiency at temperatures < 12 °C as that observed at >12 °C (77 %) monitoring time would need to be extended to 122 min or about 2 hours.