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Native fish populations often indicate the overall health of an ecosystem and that rings true for the Great Lakes population of lake trout. However, it’s no small feat to study fish across an area spanning nearly 95,000 square miles and holding 90% of our nation’s surface freshwater. To accomplish this ongoing, herculean feat, we at the U.S. Fish and Wildlife Service use innovative tools like the mass marking program, which is supported through funding from the Great Lakes Restoration Initiative.
During the middle part of the 20th century, native lake trout populations crashed in the Great Lakes. A perfect storm of stressors overwhelmed native fish populations including overfishing and harmful invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.
Learn more about invasive species , especially sea lamprey. However, after decades of work and countless partnerships, lake trout are making a comeback. Without monitoring and tracking these fish, we wouldn’t know the full impact of their recovery or the outcomes of our actions.
In 1978, scientist John Shepherd described the challenge for fisheries managers when he said, “fish are like trees, except they are invisible, and they move.� In order to “see� fish and know how they move, biologists need accurate data to inform responsible management recommendations. That’s where mass marking comes in.
The mass marking program is a collaborative effort led by the U.S. Fish and Wildlife Service to support the decision-making of state and Tribal fisheries management agencies. Each spring, the Green Bay Fish and Wildlife Conservation Office deploys specially designed trailers to federal and state hatcheries where U.S. Fish and Wildlife Service biologists circulate hatchery-raised fish through a series of tanks and tubes. Fish receive a coded wire tag and a fin clip, which helps biologists differentiate the hatchery fish from wild fish during surveys.
The pace of the process is astonishing: fish are tagged and marked at the rate of up to 8,500 individuals an hour. That’s over 130 fish per minute, which is the pace needed to meet the demand of stocking millions of these fish each spring. This work supports an annual $5.1 billion fisheries industry that includes recreational fishing, Tribal subsistence fisheries and the recovery and restoration of imperiled ​​species.
An estimated 25 million lake trout have been tagged and stocked in the Great Lakes since the mass marking program started in 2010 and benefits from the program have been experienced basin-wide.
Visit the Great Lakes Restoration Initiative page to learn more about our work.
