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RELATIVE EFFECTS OF LAMPRICIDE EXPOSURE VERSUS SEA LAMPREY PREDATION ON LAKE STURGEON POPULATION VIABILITY IN THE LAURENTIAN GREAT LAKES
Norine E. Dobiesz1
1Quantitative Fisheries Center, Department of Fisheries and Wildlife, Michigan State University, 293 Farm Lane - Room 153, Giltner Hall, East Lansing, MI 48824 -1101
Many factors have contributed to the decline and continued low abundance of Great Lakes lake sturgeon Acipenser fulvescens including commercial exploitation, reduced water quality, loss of spawning habitat, migration barriers, and climate change. There has also been concern that sea lamprey Petromyzon marinus control efforts involving the application of the lampricide 3-trifluormethyl-4-nitrophenol (TFM) has contributed to age-0 lake sturgeon mortality and may inhibit lake sturgeon recovery. Conversely, the lampricide treatments have been effective in reducing larval sea lamprey abundance leading to reduced mortality on adult lake sturgeon and other large Great Lakes fish. We evaluated the tradeoff of increased mortality on age-0 lake sturgeon due to TFM exposure against the increased mortality on adult lake sturgeon from sea lamprey parasitism using an age-structured model with new data on TFM toxicity. The equilibrium population of age 25+ lake sturgeon attained using the new TFM toxicity rates and constant sea lamprey predation mortality is 7,551 individuals. When TFM induced mortality is constant, reductions in adult mortality can produce increases of 38-114% in the maximum abundance of lake sturgeon. Because lake sturgeon have very long life spans and adults experience many reproductive cycles and are highly fecund, every adult represents a significant impact on future abundances. Therefore, management actions that reduce the mortality on adult lake sturgeon will have the greatest influence on increasing adult recruitment.