Researchers want to catch “vampire fish” using smells

GRAND RAPIDS, Michigan (WOOD) – Researchers are launching a 10-year project to keep so-called “vampire fish” out of Michigan’s rivers.

According to Michigan State University, three dams along the Boardman-Ottaway River have been removed over the past 20 years as part of a major cleanup effort. The only one remaining is the Union Street Dam in Traverse City, which lies between the river and Lake Michigan.

The dam is aging and has had unintended consequences for native wildlife, but it cannot simply be removed. Doing so would allow invasive species such as sea lampreys and others to enter the river, making controlling these populations much more difficult and expensive.

“Here in the Great Lakes, we face a unique challenge that exists in other places around the world. If we allow our rivers to reconnect freely to the lakes or oceans and other places, it increases the possibility of invasive species entering those rivers and causing harm to the species that live there,” sea lamprey expert Michael Wagner, an associate professor at MSU, told Nexstars WOOD. “There can be ecological and economic damage.”

Wagner said that although people have been trying to help fish cross dams for 400 years, “we’re still not really good at it.”

“These dams are critical to keeping this really dangerous species under control, but they also have other consequences that we want to work to contain,” he said.

The Great Lakes Fishery Commission has assembled a team of researchers from MSU and other universities to work on FishPass, a project that broke ground in May to replace the Union Street Dam with the goal of allowing fish like walleye and lake sturgeon into the Boardman-Ottaway River while keeping invasive species out.

FROM “CUTE LITTLE FISH LARVAE” TO PARASITE

Sea lampreys are native to the Atlantic basin. They arrived in the Great Lakes about 100 years ago via canal systems that connect the lakes to the St. Lawrence Seaway, Wagner said.

For most of its life, the sea lamprey is a harmless larva.

“For the first four years of their lives, they’re these cute little – cute to biologists – but cute little fish larvae that live in the sediment of rivers, feed on organic matter and actually do some positive things for the ecosystem,” Wagner explained.

But after four years, the lamprey transforms into its juvenile form and develops eyes and a mouth with countless teeth. It also stops eating things like algae and instead attaches itself to fish like lake trout and whitefish, earning it the nickname “vampire fish.”

“(They) use their toothed tongue to drill a hole in the side of the fish and then feed on blood, fluids and some tissue,” Wagner said.

The sea lamprey stays in this parasitic phase for 12 to 18 months, during which time it kills about 40 pounds of fish, Wagner said. Many of the fish it kills are ecologically, economically and culturally important in the Great Lakes region.

“Unchecked, they decimated the lake trout populations. They wiped out some native species from the system,” Wagner said. “So Canada and the U.S. came together and said, ‘We really need to get this species under control,’ and they’ve been doing that ever since with great success.”

HOW COULD FISHPASS HELP?

After 12 to 18 months, the sea lamprey finally stops feeding and migrates back to the river to spawn and die, says Wagner.

FishPass would catch the sea lamprey as it attempts to enter the river, about a month before the nocturnal, solitary animal dies of natural causes.

“How do you catch a fish that is alone at night and doesn’t eat?” asked Wagner. “You can’t just put bait on the hook.”

Sea lampreys use smells to navigate rivers and spawning grounds. Larvae produce a smell that signals to sea lampreys that it is a good habitat, and sexually mature males produce a pheromone to attract females.

However, when a sea lamprey is bitten by a predator, it releases a warning chemical that others can smell, which Wagner compared to a smoke detector.

The researchers hope that these two attractive and repelling smells will lure the sea lampreys away from the river passage and into a trap.

“From their perspective, everything is normal,” Wagner said. “The technique we’ve been experimenting with is that we can use that alarm signal to keep them away from the fish ladder and direct them to another area of ​​the stream where we can perhaps lure them into a trap with bait or other means and catch them.”

He pointed out that it was important to catch the sea lampreys, otherwise they might ignore the repulsive smell and go into the river anyway.

“They have to go upstream to spawn. They only have this one chance in their life. As they become more and more desperate to get to the spawning grounds, they might decide to ignore the risk,” Wagner explained. “Just like you might decide to ignore a smoke alarm if you have to run through the building to get out because the door is on the other side.”

The goal of the project is to eventually automate the selective passage, but for now, MSU says researchers will monitor and tag all fish that pass through the passage. Captured sea lampreys will be used for further research, public education about invasive species and in classrooms for dissection.

If the project is successful, the sorting system could be deployed elsewhere in the Great Lakes and around the world, which Wagner said would be a “crucial advance for conservation.”

“We are doing top-notch work … on a problem that we believe can be solved,” he said.