Sea Lamprey Lowermost Barriers

Over 10,000 barrier structures are known to exist on Great Lakes tributaries, however sea lamprey control agents consider fewer than 500 lowermost barriers as important to maintaining present levels of sea lamprey control. The list is expected to evolve as it is shared with a wider audience and as barriers are built, modified, or removed. The Great Lakes Fishery Commission (GLFC) has agreed to host a living list of these structures for reference at any time (www.glfc.org/pubs/slcp/lowermost-barriers.xlsx). Updates will be made on a regular basis to ensure completeness and each revision will be date stamped.This list contains only man-made structures - waterfalls were excluded. We acknowledge that some lowermost barriers are built upon natural falls that would likely block sea lamprey migrations but chose to include those structures since we cannot confirm this. Not all lowermost barriers are located on the mainstream of a tributary. Some systems have multiple lowermost barriers if the primary structure does not block lampreys 100% of the time or if lowermost barriers are located on secondary tributaries. This list contains only man-made structures - waterfalls were excluded. We acknowledge that some lowermost barriers are built upon natural falls that would likely block sea lamprey migrations but chose to include those structures since we cannot confirm this. Not all lowermost barriers are located on the mainstream of a tributary. Some systems have multiple lowermost barriers if the primary structure does not block lampreys 100% of the time or if lowermost barriers are located on secondary tributaries. This list also contains a few additional system descriptions to help describe the impact of each lowermost barrier. Length of stream blocked (km) are provided for the entire upstream watershed and to the assumed next upstream barrier. All barriers included in the National Inventory of Dams or the Ontario Dam Inventory were considered candidate second order barriers. We acknowledge that these inventories are not comprehensive and are working toward validating and updating next upstream barriers. We estimated upstream lengths using the National Hydrography Plus High-Resolution Dataset (NHDPlus HR) and associated nhdplusTools R package (Blodget, 2018; nhdplusTools: Tools for Accessing and Working with the NHDPlus, U.S. Geological Survey, Reston, VA). Finally, we have included estimates to treat any newly opened stream segments with lampricides using a model developed by sea lamprey control agents. This model incorporates length of stream, watershed area, and stream alkalinity to estimate staffing and lampricide costs (in USD). This simple, deterministic bioeconomic assessment is meant to provide a starting point for future discussions regarding investments in selective fish passage and barrier removal or construction negotiations. Assessments incorporating increased ecological and economic realism and stochastic model elements would be valuable future work. For more information regarding this work, please see the following citation: Hrodey, P.J., Lewandoski, S.A., Sullivan, W.P., Barber, J.M., Mann, K.A., Paudel, B., Symbal, M.J., 2021. Evolution of the sea lamprey control barrier program: The importance of lowermost barriers. Journal of Great Lakes Research 47, S285–S296. https://doi.org/10.1016/j.jglr.2021.10.006