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Scientists eavesdrop on an ancient river giant: the lake sturgeon

MARY LOUISE KELLY, HOST:

There are prehistoric giants gliding through the depths of some U.S. rivers. A type of fish called lake sturgeon has been around since the time of the dinosaurs. But in the past century, populations have plummeted. As St. Louis Public Radio's Shahla Farzan reports, Missouri scientists are using tracking devices on this endangered species to try to prevent its extinction.

SHAHLA FARZAN, BYLINE: The lake sturgeon is a strange-looking fish with a curved snout, tail like a shark and long whiskers near its mouth. Adults can be huge, growing longer than a king-size bed and weighing hundreds of pounds.

SARAH PEPER: They're just very strong, powerful fish, so they start thrashing around. It's hard to hold onto.

FARZAN: Sarah Peper is a state fisheries biologist in Missouri. In April, as she was getting ready for church, she got an urgent phone call from a colleague - lake sturgeon were spawning along the banks of the Mississippi River near St. Louis, where we're now standing. Peper has been studying lake sturgeon for years, but she had never seen the fish reproduce in the wild. On that day, she and other scientists watched as the fish congregated in the shallows, thrashing their tails and releasing peppercorn-size eggs.

PEPER: And it was like we had a little sturgeon spawning party on the shoreline. We were all just so excited.

FARZAN: Lake sturgeon were once found in waterways ranging from Minnesota to Tennessee, but populations have plummeted in the past century, and the species is now listed as endangered in nine states. Lisa Izzo is a fisheries researcher at the University of Wisconsin, Stevens Point. She says because sturgeon take years to mature, overfishing has decimated some populations. But she adds that river dams are also to blame.

LISA IZZO: The dams in a lot of these systems cut off their access to that really high-quality spawning habitat, so they weren't able to reproduce as successfully.

FARZAN: Izzo and others say protecting spawning sites is critical for sturgeon conservation. But where are these fish going to spawn? That question has long stumped scientists because lake sturgeon can be hard to find.

IZZO: It's not like you can just put a net out there and catch 20 or 30 fish.

FARZAN: Researchers in Missouri are using technology to track sturgeon during spawning season. This spring, they captured adults and implanted radio transmitters under the silvery skin of their bellies. On an April morning, Peper and two other scientists climb into a boat in the Mississippi River.

PEPER: Everybody, aboard. Everybody, life vests.

FARZAN: They submerse microphone in the water, listening for tagged fish. A radio receiver pings when a sturgeon is nearby.

PEPER: OK, and it - so we just heard a fish, and it was a strong enough signal to give us a number.

FARZAN: Each tag has its own ID. This fish, Number 22462, was tagged three years ago in Iowa. Army Corps biologist Ryan Swearingin says by tracking the movements of individual fish, scientists hope to pinpoint habitats to protect.

RYAN SWEARINGIN: We can help keep this area as hospitable as we can during that prime spawning period.

FARZAN: The project is just one piece of a larger effort to bring lake sturgeon back from the edge of extinction. So far, Peper says, sturgeon have survived cataclysmic events over 150 million years.

PEPER: You know, we had the asteroid that killed the dinosaurs. We had continents crashing into each other and pulling apart. And these fish survived all of that.

FARZAN: But, she says, lake sturgeon may not survive us unless we take action now to protect them.

KELLY: Shahla Farzan, and this is NPR News. Transcript provided by NPR, Copyright NPR.