Someday these will grow into the biggest fish in North America, but for now, they’re the precious cargo of a state program to bring these freshwater giants back to their native habitat. (Read more about the world’s giant fish.)
Water Currents: Rebirth of Lake Sturgeon: Freshwater Species of the Week
Posted 18 May 2013 - 10:00 AM
Topping six feet (two meters) long and weighing nearly 200 pounds (90 kilograms), lake sturgeon once roamed rivers and lakes of the Mississippi River, Hudson Bay, and the Great Lakes. Unchanged from prehistoric times, the lake sturgeon has unusual features not seen in today’s fish, including an external skeleton that gives it an armored appearance.
But this ancient survivor has had trouble fending off human threats, including overfishing in the late 1800s, dams that have blocked migrations, and industrial pollution that has poisoned the fish’s spawning grounds. (Learn more about freshwater threats.)
Today there are genetically unique populations of sturgeons in at least eight rivers around Lake Michigan, with about 166 fish in the Kalamazoo River, according to Kregg Smith, senior fisheries biologist at the Michigan Department of Natural Resources.
No one knows how many fish once lived in the Kalamazoo. But Smith and others did know the fish—deemed a threatened species in Michigan—needed a helping hand.
So, starting in 2003, Smith and a team of nonprofits, the U.S. Fish and Wildlife Service, and native tribes set up the streamside rearing facility, which raises juvenile fish and releases them back into the rivers. So far they’ve sent 116 young fish back into the river, where they’ll eventually end up in Lake Michigan.
No Place Like Home
Inside the Kalamazoo River facility—a small trailer near a stand of trees a few hundred feet from the river’s banks—and USFWS fisheries biologist Elliott Kittel is showing me an image of a sturgeon egg zoomed in on a laptop.
Just days from hatching, I could see its curved backbone and healthy, clear yolk sac. In the wild, most of these babies wouldn’t make it—a female sturgeon can spawn millions of eggs, and “99.9 percent mortality is a good day,” Kittel said.
But eggs and larvae brought up in the rearing facility have better odds, since they’re less vulnerable to predation, disease, and starvation.
The sturgeon team’s strategy centers around rearing the young fish in water pumped from the Kalamazoo River, thus “imprinting” the juveniles with the chemical signature of the river. (Test your freshwater IQ.)
Sturgeon live most of their lives in lakes, but are born in rivers and return to the same place to spawn—for males, that’s every two years; for females, every four to six. So the biologists hope that when the human-raised sturgeon grow old enough to spawn, they’ll “home” to the place where they were born.
This reduces the possibility that sturgeon will wander into other rivers, where the wayward fish could breed with other populations, diluting their genes. (See other pictures of megafishes around the world.)
As another backup, scientists take eggs that are naturally spawned by females living in the Kalamazoo and raise them in the rearing facility.
Males are sexually mature at 10, but females don’t start breeding until about 22 years of age. Sturgeons are incredibly long-lived, sometimes reaching over a hundred: A specimen caught in Canada in 1953 was 152 years old, according to a 1954 article in the Milwaukee Journal.
Once the babies hatch, the biologists get them up to about 6 to 10 inches (15 to 20 centimeters) long, tag them, and release them into the river in the fall. The team then monitors the fish to see if they return to the river to spawn.
But the sturgeon team will have to wait until 2021—when the first released males turn 10—to see if they come back, Smith said.
To the people trying to save this unusual fish, there’s just something about sturgeon.
Ron Clark, a volunteer with the nonprofit Kalamazoo River Sturgeons for Tomorrow who was helping out at the Kalamazoo facility, said that being part of an effort to save such an ancient species “intrigued me.”
Clark, who has found the fish docile and easy to handle, said they seem to have individual personalities … they’re more like a [mammal] than a fish.”
Fisheries biologist Smith added that he likes the look of the prehistoric fish and its weird adaptations. For example, sturgeons have spiracles, which are holes in the side of the fish that allow them to breathe along with their gills.
He added that bringing the sturgeon back would give the public a chance to learn about a fish that had to survive during the dinosaur era.
“It’s the most unique fish in the Great Lakes.”
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