Scientists work to repopulate lake sturgeons

A fish whose ancestors date back at least 200 million years — possibly 300 million — came close to extinction 100 years ago. Lake Erie was once home to more of those fish than all of the other Great Lakes combined.

Today, the lake sturgeon is still listed as a threatened species in Ohio, which means anglers lucky enough to catch one must snap a photo and release it — quick. But a group of scientists plan to spend the next few decades replenishing populations of this ancient fish, particularly in the lake where they were once so plentiful.

Chris Vandergoot, director of the Great Lakes Acoustic Telemetry Observation System and an associate professor at Michigan State University, is one of those scientists who seeks to reverse the damage done to the prehistoric species by humans.

Damage

The damage started in the early 1800s, when commercial fishermen seeking whitefish, lake herring or cisco also caught lake sturgeon in their nets. But the sturgeon’s bony plates, and the toothlike denticles that project from them, destroyed the fishermen’s nets. That made the sturgeon a nuisance fish.

Some were used to make oil for boat fuel, but most were just discarded, Vandergoot said. Then the fishermen figured out how to make stronger nets. And by the mid-1800s, the sturgeon they caught became valuable for their meat but even more for their eggs, which were made into expensive caviar.

In the last two decades of the 1800s, an average of four million pounds of sturgeon were caught in the Great Lakes each year. In 1879, five million pounds were caught in Lake Erie alone, according to the U.S. Fish and Wildlife Service.

By the first two decades of the 20th Century, the over-fishing of lake sturgeon stopped because so few remained, Vandergoot said.

Repopulating

Now GLATOS and its partner agencies — the Ohio Division of Wildlife, U.S. Fish and Wildlife Service, Toledo Zoo, University of Toledo and U.S. Geological Survey — are harvesting lake sturgeon eggs for a different reason: repopulating their species.

Three years ago, they began collecting eggs from where Lake Huron empties into the St. Clair River, a place where lake sturgeon are fairly plentiful. They gave half of the eggs to the Toledo Zoo and other half to the Genoa National Fish Hatchery in Wisconsin.

In 2018, about 3,000 young sturgeon between 6-8 inches long were released into the Maumee River, in front of an audience of more than 1,000 people. Several hundred people attended — and helped with — the second release in 2019. Several dozen of the fish released were fitted with high-tech transmitters. The rest had something that resembles the chip you put in a pet.

Collecting information

Meanwhile, GLATOS had installed about 1,500 receivers in the Great Lakes, including about 200 that are spread out all over Lake Erie from the western basin near Toledo to the eastern basin near Buffalo, New York. Once a year, those receivers are pulled from the bottom of the lakes and their data is downloaded.

The receivers pick up signals from the sturgeon as they swim by, as well as other species of fish that have been fitted with transmitters such as walleye, grass carp and yellow perch. Each fish has its own number that identifies it by species, age, sex and other factors.

“It’s like the E-ZPass system on the Turnpike,” Vandergoot said.

Information that receivers revealed about the “class of 2018” sturgeon was encouraging, he said.

It showed that they left the Maumee River within a week of being released, and that most were still swimming around the western basin almost a year later. Once scientists determine the youngsters’ survival rate, it will help them figure out how many sturgeon they need to release each year — for many, many years to come.

“We’re looking at how many fish we need to stock over the next 10 to 20 years to sustain the population in the future,” Vandergoot said.

Lifespan

The reason they must look so long into the future has to do with the lake sturgeon’s lengthy lifespan. Male sturgeon live an average of 55 years, while females live between 80 and 150 years, according to the U.S. Fish and Wildlife Service.

But that means it takes them much longer than other fish to reach sexual maturity — eight to 12 years for males and 14 to 33 years for females, said Roberta Muehlheim, assistant curator of vertebrate zoology for the Cleveland Museum of Natural History.

And just because they’ve reached sexual maturity, it doesn’t mean they will reproduce every year. Female lake sturgeon only mate once every four to nine years, males every two to six years, Muehlheim said. To make up for their sporadic love life, females are capable of producing a million eggs in one spawning.

“The eggs are laid on the bottom, where they stick. But then the fish just leave them; there’s no parenting,” she said. “They essentially put more eggs in the basket to ensure survival.”

Primitive

Muehlheim, who had some experience with lake sturgeon during her 20 years at the museum, finds the species fascinating.

“They are the most ancient fish we have in Lake Erie,” she said.

Fossils of the family go back to the Cretaceous period, when dinosaurs were at their peak. A recent study at the University of Pennsylvania found that a 300-million-year-old fossil, which was thought to be unrelated, may actually be an ancestor of the sturgeon, Muehlheim said.

“They are a very primitive fish,” she said. “But primitive doesn’t mean simple, archaic, or out of date. It means they hit on the right design at an early point in their evolution and have had few major changes in the past 200 million years.”

Like whiskers that sense snails, mussels, small fish and other food items hidden beneath the silt, and a protractible mouth designed to vacuum them up. No teeth? No problem. A pallet covered with cartilage, and a muscular throat, grind up the food and make it digestible.

And then there are those bony plates and pointy things that used to tear up nets. They serve as armor to protect the sturgeon in its first years of life. But armor has a cost in energy — not to mention friction — as the sturgeon glides along the bottom. When it grows big enough not to be worried about predators, it absorbs most of the plates back into its body, Muehlheim explained.

And since, according to the FWS, lake sturgeon can grow to nine feet long and weigh 300 pounds, they probably don’t worry too much about predators.

“They hit on what works for them early in their history,” Muehlheim said of the colossal but very efficient species. “In that respect, it’s a lot like the crocodile.”