DETROIT, MI (WOWO) The population of invasive sea lamprey in the Great Lakes has declined after regular control efforts resumed following disruptions during the COVID-19 pandemic, according to a new report from the Great Lakes Fishery Commission.

Michigan Public reports surveys conducted by the commission show lamprey numbers have returned to pre-pandemic levels across most of the Great Lakes. During the pandemic, treatments were limited because of border closures and other restrictions, allowing the invasive species to spread more widely.

Sea lamprey are native to the Atlantic Ocean and are considered one of the most damaging invasive species in the Great Lakes. They attach to fish and feed on blood and bodily fluids, weakening or killing their hosts. Each lamprey can consume large amounts of fish over its lifetime, and females can produce tens of thousands of eggs.

The Great Lakes Fishery Commission, created in the 1950s, is responsible for coordinating lamprey control to protect the region’s fisheries. The commission works with Fisheries and Oceans Canada, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey.

Control efforts include the use of lampricides applied to streams to eliminate juvenile lamprey before they begin feeding. Officials say the treatments are designed to target lamprey without harming other aquatic species. Barriers, including electric and bubble systems, are also used to limit lamprey movement into spawning areas.

According to the report, the three-year average lamprey population declined in all of the Great Lakes except Lake Superior. Officials say continued monitoring and treatment are planned to maintain the downward trend and support the Great Lakes fishing industry and regional economy.

The commission says sustained funding and coordinated international efforts remain key to preventing future population increases.