The U.S. Fish and Wildlife Service this week announced that lake sturgeon, which find refuge in the St. Croix River, will not be listed under the Endangered Species Act. The decision comes after an environmental nonprofit sued the agency to designate the species in order to protect the fish and dedicate more resources to their restoration.

Lake sturgeon once swam waters throughout much of North America, including the Great Lakes and Mississippi River systems. Not only did they range across large parts of North America, but they existed in huge populations. Their numbers were decimated during the nineteenth and early twentieth centuries, primarily by overharvest and the construction of dams, which disrupt their reproductive cycle.

In 2018, the Center for Biological Diversity asked the U.S. Fish and Wildlife Service to assess the sturgeon population, and consider it for endangered listing. Six years later, they have a decision. It took a lawsuit in 2021 to spur the agency into action on completing the assessment.

The Fish and Wildlife Service now says restoration efforts including widespread stocking of the fish have paid off, and the fish is not at peril of eradication.

“Today’s announcement shows the power of collaborative conservation and the impact it can have for species like the lake sturgeon,” said Midwest Regional Director Will Meeks. “The fact that we’re seeing more and more lake sturgeon populations spawning in their historical habitat is a clear sign that restoration efforts are progressing. This success is credited to many partners including states, Tribes, local organizations and others across the country coming together to conserve this species.”

Sturgeon still exist in fairly high numbers in some waters, including the St. Croix and its tributaries. Its largest tributary, the Namekagon, gets its name from the Ojibwe language, translating roughly to “place of the sturgeon.” The largest sturgeon caught in Minnesota was in the Kettle River, a St. Croix tributary, in 1994. It weighed 94 lbs and was measured at 70 inches — nearly six feet long. The state catch-and-release record was a 78 inch fish caught in Lake St. Croix through the ice in 2019 by Darren Troseth.

The St. Croix remains an exception, though. Sturgeon populations are still low in the Mississippi River and many of its tributaries.

“The current status of Lake Sturgeon throughout the Mississippi basin is considered to be severely depressed from historical abundance levels,” wrote experts from the International Union of Concerned Scientists in a 2019 assessment, which declared the fish to be globally endangered.

Sturgeon are designated by the state of Minnesota as a “species of special concern.” The state also allows some fishing for the species, with a catch-and-release season increasingly popular on the lower St. Croix and other rivers. Anglers can harvest one fish per year with a special tag that must be purchased from the Department of Natural Resources.

Sturgeon are often referred to as “prehistoric” for their appearance and natural history. The fish first appeared in the fossil record some 150-200 million years ago, and retain their primitive biology and appearance, including bony plate-armored covering and “whiskers” near their mouth that help them feel for food. They can live more than 100 years. They also don’t start breeding until between 15 and 30 years of age, making it even more difficult to protect their populations.

Despite its decision not to list the fish as endangered, the Fish and Wildlife Service did acknowledge threats to sturgeon’s survival.

“The primary threats affecting the lake sturgeon’s biological status are dams, barriers, and climate change,” the agency wrote in its decision. “Dams and barriers occur across the lake sturgeon’s range and can block access to spawning and nursery habitat, stopping lake sturgeon from completing their life cycle, thus making this the most significant threat to the species.”

But the agency also said it believes that populations that are growing today will continue to grow in the future, thanks to stocking and other efforts. While few dams are expected to be removed anytime soon, conservation and restoration efforts by states, tribes, and other organizations will continue until they’re no longer needed.