Sea lamprey invades, harms fish in Lake Superior


The sea lamprey, one of the most damaging aquatic invasive species, has taken up residence in Lake Superior.

Aquatic invasive species are non-native plants, animals and pathogens that live primarily in water and thrive in their new environment. They can cause harm to the economy, environment and also human health.

“The sea lamprey is Lake Superior’s worst aquatic invasive species,” said Sharon Moen, Minnesota Sea Grant’s science writer.

A sea lamprey is an aquatic vertebra that is native to the Atlantic Ocean. Their looks resemble those of an eel, and they can live in both fresh water and salt water.

Sea lampreys were introduced into the Great Lakes through shipping canals in the early 20th century.

“They out-compete native species for food and also for breeding space and territorial space,” Moen said.

Sea lampreys can attach to fish with their disk-shaped mouth, which is full of teeth. They prey on almost all the species' of fish in Lake Superior, including walleye, rainbow trout, and sturgeon.

“We spend millions of dollars each year controlling sea lamprey in the Great Lakes, and that’s just one species,” Moen said.

According to Doug Jensen, aquatic invasive species coordinator at Minnesota Sea Grant, $21 million is spent every year controlling aquatic invasive species across the Great Lakes region.

Aquatic invasive species such as the sea lamprey can be transferred to lakes in a variety of ways, including through humans, ships and other watercrafts.


“The sea lamprey came in because we opened up waterways to bypass some of the waterfalls such as Niagara Falls, which previously blocked lamprey migration,” said Jeff Gunderson, director of fisheries and aquaculture for the Minnesota Sea Grant.

Another way aquatic invasive species are transferred from lake to lake is through ballast water. The large ships that haul coal, grain and other material are unstable when they are empty. In order to stabilize the ship, they fill their tanks with water.

When ships arrive to their assigned port to pick up their product, they discharge the water they picked up, and it can contain species from the location where the water was taken on board. In an effort to prevent aquatic invasive species transfer through ship’s ballast water, ships entering the Great Lakes have to exchange their ballast water.

“If a ship in a European port takes on ballast water and starts heading to Duluth, in the middle of the ocean somewhere, they have to pump out all the fresh water and take on salt water,” Gunderson said.

This procedure helps in a couple of ways. First, it pumps out some of the invasive species, and second, the salt water kills most of the remaining invasive species left in the ship.

In 1990, the Nonindigenous Aquatic Nuisance Prevention and Control Act (NANPCA) was passed. It is “an act to prevent and control infestations of the coastal inland waters of the United States by the zebra mussel and other nonindigenous aquatic nuisance species, to reauthorize the National Sea Grant College Program, and for other purposes.”

The shipping industry views ballast water as a major problem, according to Moen, and the treatment of this water is now being more thoroughly examined.

“There are new ballast water regulations now in the United States that will require incoming salt water ships to have ballast water treatment technology on board,” Moen said.

Ships that are headed toward port that don’t require the use of ballast water have to go through a process called ‘spit and swish.’ This simply means that the ships have to take on salt water, swish it around, and then discharge it back into the ocean.

“It’s very complicated because it’s hard to measure the number of organisms and determining if they are alive or not,” Gunderson said.


Thanks to these processes and new ballast water laws, less ballast water has been let loose into the Great Lakes.

“No unmanaged ballast water has been discharged into Lake Superior since 2009,” Jensen said.

Another way invasive species enter Lake Superior is by people who pour out their aquariums into the lake. Aquarium fish can carry diseases that kill native fish. Aquarium plants can snag boat propellers and clog waterways.

A national public awareness campaign called Habitattitude was launched in 2004 and targets aquarium hobbyists, water gardeners and backyard pond owners. Its goal is to encourage these people to prevent the release of unwanted aquatic plants, fish and other animals.

Another organization fighting against aquatic invasive species is the Minnesota Sea Grant, which is the only Sea Grant program focused entirely on Lake Superior. It seeks to maintain and enhance its coastal environment and coastal economy through high-quality research, education and outreach.

“Here at Sea Grant, our mission is primarily education,” Moen said.

Some of the issues, besides invasive species, that the Minnesota Sea Grant deals with are shipping, climate change, sustainable urban development and water quality.

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