Sturgeon reintroduction initiative yields promising first-year survival rate

Ecologists celebrated the release of thousands of palm-sized lake sturgeon into northwest Ohio's Maumee River in 2018, kicking off an ambitious two-decade plan to re-establish the ancient species in the waters it once called home.

More than five years later, it’s still too soon to declare success. But early signs are promising, according to recent research led by The University of Toledo and published in the peer-reviewed North American Journal of Fisheries Management.

The research tracked the first-year survival rates for cohorts released in 2018, 2019 and 2021, with results suggesting that the initiative is on track to achieve its goal of a self-sustaining population of 1,500 naturally reproducing lake sturgeon in the Maumee River – hopefully – by 2038.

“If they survive at this age, it’s a really good sign,” said Dr. William Hintz, an associate professor of ecology based at UToledo’s Lake Erie Center in Oregon, Ohio. “Once they grow beyond the first-year stage, their survival rates are high. At that point it becomes likely they will become adults and hopefully stick around.”

Lake sturgeon were once abundant in the Maumee River, but have faced significant population declines due to habitat loss, overfishing and pollution since the 1800s. This result was extirpation from the Maumee River and endangerment across Ohio.

UToledo has long been engaged with the reintroduction initiative alongside federal and state partners and the Toledo Zoo, with faculty and students evaluating habitat conditions in the Maumee River well before the first fingerlings were released in 2018.

The reintroduction initiative aligns with a broader area of research excellence at UToledo, where scientists, engineers, doctors and public health experts are engaged in numerous facets of water quality research. These include the ecologists at UToledo’s Lake Erie Center, who study local environmental conditions and aquatic resources as a model for the Great Lakes and aquatic ecosystems worldwide.

Hintz and Jorden McKenna, who graduated with a master’s degree in ecology and organismal biology in 2023 and now works as a biologist with the U.S. Fish and Wildlife Service, join colleagues at the U.S. Fish and Wildlife Service, the U.S. Geological Survey, the Ohio Department of Natural Resources, the Michigan State University Department of Fisheries and Wildlife and the Toledo Zoo as co-authors on the recent research in the North American Journal of Fisheries Management.

It analyzes data gathered through acoustic transmitters that are implanted in a subsample of sturgeon that are released into the Maumee River. These transmitters track fish survival and movement by pinging receivers that are strategically positioned throughout Lake Erie under the Great Lakes Acoustic Telemetry Observation System.

The researchers’ analysis suggests an annual survival rate between 19% and 71% for the three cohorts of approximately 3,000 sturgeon each that were released in 2018, 2019 and 2021.

“The survival rate looks promising,” Hintz said. “The fish aren’t all dying. They’re surviving at a rate that if we keep stocking them for 20 years, we’d hopefully reach our target population of 1,500 naturally reproducing adults.”

One important caveat? Survival is only half of what’s needed to successfully establish a self-sustaining population of lake sturgeon in the Maumee River.

Hintz explained that ecologists are also counting on the fish to imprint on the unique chemical signatures of the river and return to it to spawn, similar to the process that drives Pacific salmon back to their natal streams across the western United States and Canada.

But that won’t happen until the sturgeon, whose lifespans routinely pass a half-century, reach sexual maturity at 12 to 15 years old — still  several years away even for the first cohort that ecologists reintroduced in 2018.

“Maybe by 2030 or 2032, we might be able to see some adults coming back,” Hintz said.