ANN ARBOR, MICHIGAN – The Great Lakes Fishery Commission (GLFC) reported last week that populations of the invasive, parasitic sea lamprey remain at near-historic lows in Lakes Michigan and Ontario, and above target, but holding steady, in Lakes Huron, Superior and Erie.
Sea lamprey populations in Lake Huron are close to target levels and have been holding steady for the past five years. Abundances in Lakes Superior and Erie remain above target but have also decreased significantly since the near-recorded highs observed in 2017. Sea lampreys are the worst of the alien species to invade the Great Lakes. Before control, sea lampreys destroyed many times the human fish catch. Today, sea lamprey control is the foundation of the $7 billion Great Lakes fishery, a GLFC release from November 12 explained.
The Commission and its partners are encouraged by the overall decrease in abundance of sea lampreys throughout the Great Lakes basin during 2019, but caution that environmental conditions, such as a prolonged spring and high precipitation events, contributed to the decrease.
Sea lampreys are native to the Atlantic Ocean but have been an unwelcome nemesis in the Great Lakes since they invaded through man-made shipping canals in the early 20th century. By 1939, sea lampreys were ravishing the system and laying waste to millions of fish. They do little good for the Great Lakes ecosystem as they prey on important species and have no natural predators. The average sea lamprey will kill up to 40 pounds (18 kg) of fish during its parasitic stage. Sea lampreys prefer trout, salmon, whitefish and sturgeon, but they also attack smaller fish like walleye and perch.
Sea lampreys successfully reproduce in more than 500 Great Lakes tributaries and thus, the battle to keep their populations in check must remain steadfast. Thanks to more than six decades of successful sea lamprey control, the Great Lakes fishery is worth $7 billion annually to the people of Canada and the United States today. Before control, sea lampreys killed an estimated 103 million pounds (47 million kilograms) of fish per year. Today, because of ongoing control, sea lampreys kill less than 10 million pounds (4.5 million kilograms) of fish per year. Sea lampreys are a coiled menace; they are extremely hardy and relentless, and history has shown that if control efforts are ceased, or even relaxed for a short period of time, their populations will rebound and the fishery will suffer.
The Great Lakes Fishery Commission was established by the Governments of Canada and the United States in 1955 as a response to the catastrophic damage wrought by the sea lamprey invasion. Sea lamprey control consists of several techniques including lampricides, barriers and traps. The Commission also is evaluating the use of chemosensory cues as means to influence migratory and spawning behaviours. For more information, visit www.glfc.org/sea-lamprey.php.
“Keeping sea lamprey populations in check is absolutely critical if we want a fishery in the Great Lakes,” said Jim McKane, chair of the GLFC. “Each year, we must wage the battle anew. We cannot rest on our laurels or rely on our past success. Sea lampreys are here to stay. Fortunately, we can control their populations such that the damage they inflict on the fishery is a fraction of what it once was.”
Mr. McKane added, “it is estimated that only one in seven fish will survive a sea lamprey attack. Sea lamprey abundance targets are our benchmarks for a healthy fishery-targets for each lake were determined based on the average number of sea lampreys across a five-year period when wounding rates were deemed acceptable. We continually strive to reach and maintain a level of sea lamprey suppression that allows for the establishment of a fishery that supports the millions of people that live, work and recreate in the Great Lakes.”
“The Great Lakes sea lamprey control program is the most successful aquatic vertebrate pest control program administered at an ecosystem scale in the world,” said Doug Stang, the Commission’s vice-chair. “It’s effectiveness is built upon partnerships with both federal governments, the US states, the province of Ontario, tribes and the Commission. The fishery makes these lakes great, and without sea lamprey control, there would be no fishery.”
For nearly a decade, heightened and targeted treatment strategies, including two large-scale treatments of the St. Mary’s River, have been employed in Lake Huron. While sea lamprey abundances are slightly above target, they are still near historic low and are holding steady. Two tributaries to northern Lake Huron, the Mississagi and Garden Rivers, have been a focus of the control program. The Mississagi was treated in 2019 in partnership with the Mississauga First Nation and the Garden River will be treated in 1920, as part of an ongoing alliance with the Garden River First Nation. The GLFC expect the benefits of these treatments to be seen in the 2021 population numbers.
