Prioritizing lampricide treatments in Great Lakes tributaries and lentic areas during 2000–2017

Abstract

The sea lamprey (Petromyzon marinus) is an invasive species in the Laurentian Great Lakes which requires control to protect valuable fisheries. The Sea Lamprey Control Program (program) uses chemical methods (lampricides) each year to treat infested streams, but limited resources only allow control agents to target 100–125 streams annually. To provide the most cost-effective use of these resources, the program began using the Empiric Stream Treatment Ranking (ESTR) system in 2000 as a decision support tool for selecting streams for treatment. Following a comprehensive review of larval assessment techniques in 2002, the program transitioned from a labor-intensive quantitative technique to a more rapid catch-per-unit-effort based approach. Staff resources were re-allocated to lampricide control, allowing for treatment of more streams annually. Beginning in 2009, stream selection shifted to cost-per-kill of large larvae (>100 mm) and incorporated expert opinion along with targeted treatment strategies. This resulted in a greater number of treatments on an annual basis overall as well as increased treatment frequency for many individual streams. The average adult sea lamprey index decreased by 26% and lake trout wounding rates decreased by 21% across the Great Lakes basin during 2010 to 2017 when compared to 2000 to 2009. Recommended improvements to the stream selection model include: leveraging historic data and expert knowledge to identify streams for treatment, refining the accuracy of the ESTR decision tool, incorporating supplemental and alternative control methods into the treatment selection process, and identifying areas to improve larval assessment techniques that guide and evaluate lampricide control efforts.