Editor’s note: Last month, the Department of Natural Resources reported 60 endangered and 60 threatened species in Michigan. This week, in honor of Earth Day, we will share the stories of some of these animals and the work being done to help save them.

GRAND RAPIDS, Mich. (WOOD) — The lake sturgeon is a unique creature that stands out from its fellow fish in many ways.

Not only is it an ancient fish — believed to have been around in a similar form for more than 100 million years — but the lake sturgeon is also the largest native species to the Great Lakes. They have been measured longer than 6 feet and more than 200 pounds. They live for decades. According to the National Wildlife Federation, the average lifespan for males is around 55 years, but females can live up to 150 years. Unlike most fish, lake sturgeon don’t have scales but a coarse skin. And even the name is misleading, because lake sturgeon are regularly found in rivers, as well.

While they aren’t a common sight now, lake sturgeon once ruled the Great Lakes region. Numbers have dropped off harshly over the last 200 years, primarily thanks to overfishing in the 19th and early 20th centuries. And they face several other challenges, including pollution, loss of primary food sources and impacts from invasive species.

Lake sturgeon were designated as a threatened species in Michigan in 1994, kickstarting conservation programs to protect the fish and help regenerate the population.

While those conservation efforts first focused on other areas of the state, a compilation of researchers have turned their attention to the Grand River system in West Michigan, surveying for lake sturgeon and monitoring for breeding cycles.

The John Ball Zoo is working alongside the Grand Rapids Public Museum, Grand Valley State University, the Grand Valley Metro Council, the U.S. Fish and Wildlife Service and a consulting firm to conduct the surveys.

Bill Flanagan, the conservation manager at John Ball Zoo, said sturgeon are a difficult fish to study because they are notoriously elusive.

“The first step for us for conservation is just knowing how many are there. And it’s hard to count a fish like that. It lives on the bottom, it’s pretty secretive, and the Grand River is pretty big and wide, so it’s not easy to survey,” Flanagan told News 8.

Adult lake sturgeon live out in big lakes like Lake Michigan, but they swim upriver to spawn. The juvenile sturgeon live in rivers for the first year of their lives before moving out to the lakes.

The team has been conducting surveys for four years. This past summer, it announced a major breakthrough: confirmation that lake sturgeon are using the Grand River as a breeding ground.

Flanagan said the survey team found six juvenile sturgeon in the river last year.

“It means not only are there sturgeon present in the river, but it means they are reproducing, too,” Flanagan said.

GRPM researcher Stephanie Ogren said that finding juvenile sturgeon is also a good sign for the health of the river system.

“It kind of is sort of a ‘sensor’ for the rest of the species,” Ogren told News 8 last September. “If sturgeon are doing well, you can guess most species are doing OK. If sturgeon are having a hard time, you may have some issues with the river system.”

The next step for the research team is to get a better idea of the population of sturgeon coming to the Grand River system to spawn.

“We’re working with Grand Valley State University to install a sonar system that will help us count the adult sturgeon in the river, which will be really important for finding out what the sturgeon population is,” he said. “Finding out how many are there (helps us understand) the scope of the problem and how we can help.”

Harvesting lake sturgeon is extremely limited and only allowed in a handful of waters. Lake sturgeon cannot be legally harvested from the Grand River system.

Flanagan asks anglers to be mindful of their fishing haul and to understand that they are dealing with a threatened species. If you do catch a sturgeon, follow up with the DNR to pass along potentially relevant data.

“The DNR is always interested in hearing about rare species that you find,” Flanagan said. “Take a picture. Then, you have some data that you can share with the DNR and other biologists in the area.”

This story is the second part of a five-part series. You can read part one here.