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Tracking transformation of low-density populations of larval Sea Lampreys in streams tributary to lakes Huron and Michigan following treatment with lampricides
1 U. S. Geological Survey, Great Lakes Science Center, Hammond Bay Biological Station, 11188 Ray Road, Millersburg, MI 49759
2 Department of Fisheries and Wildlife, 13 Natural Resources Building, Michigan State University, East Lansing, MI, USA 48824-1222
3 U. S. Fish and Wildlife Service, Ludington Biological Station, 229 S. Jebavy Drive, Ludington, MI 49431
4 Department of Fisheries and Oceans, Canada, Sea Lamprey Control Centre, 1219 Queen Street East, Sault Ste. Marie, ON P6A 6W4
5 U. S. Fish and Wildlife Service, Marquette Biological Station, 3090 Wright St., Marquette, MI 49855-1699
Sea lamprey (Petromyzon marinus) control in the Great Lakes primarily involves application of lampricides to streams where larval production occurs to kill larvae prior to their metamorphosing and entering the lakes as parasites (juveniles). Because lampricides are not 100% effective, larvae that survive treatment may metamorphose before streams are again treated. Larvae that survive treatment have not been widely studied, so their dynamics are not well understood. We tagged and released larvae in six Great Lake tributaries following lampricide treatment and estimated vital demographic rates using multistate tag-recovery models. Model-averaged larval survivals ranged from 56.8 to 57.6%. Model-averaged adult recovery rates, which were the product of juvenile survivals and adult sampling efficiencies, ranged from 6.8 to 9.3%. Using stochastic simulations, we estimated production of juvenile sea lampreys from a hypothetical population of treatment survivors under different growth conditions based on parameter estimates from this research. For fast-growing populations, juvenile production peaked 2 years after treatment. For slow-growing populations, juvenile production was approximately one-third that of fast-growing populations, with production not peaking until 4 years after treatment. Our results suggest that population dynamics of residual larval populations are very similar to that of untreated larval populations. Consequently, residual populations do not necessarily warrant special consideration for the purpose of sea lamprey control and can be ranked for treatment along with other populations. Consecutive annual lampricide treatments, which are under evaluation by the sea lamprey control program, would be most effective for reducing juvenile production in large, fast-growing populations.