As Wisconsin biologists tracked the nation’s largest lake-sturgeon spawning run in April, they knew they wouldn’t see the record female fish they netted in 2012.
That monstrous sturgeon was still carrying eggs when a Department of Natural Resources crew netted it 11 years ago below the Shawano Dam on the Wolf River. When the crew pulled her onto their hammock-like cradle and suspended her below the scale, the old girl weighed 240 pounds. The DNR measured her at 87.5 inches, and declared her the largest lake sturgeon ever documented in the United States, and possibly the world.
But that wasn’t the first time DNR biologists handled the leviathan. A coded fin tag identified her as the same sturgeon a previous crew captured in 2004 at the same dam when she measured nearly 85 inches.
The last time the DNR handled the giant fish was February 2019 during the annual spearing season on Lake Winnebago, 60 miles to the southeast by crow and 100 miles by sturgeon. A lucky spearfisherman hauled the fish onto Winnebago’s ice that day and brought her body to a DNR registration station. Biologists recorded her final stats as 171 pounds and 85.5 inches, or 69 pounds lighter and 2 inches shorter than in April 2012.
Margaret Stadig, the DNR’s chief sturgeon biologist, said the big fish hadn’t shrunk. Stadig explained that the old female would have made the spawning run two months later with thousands of other lake sturgeon, and hadn’t yet maximized her spawning potential.
Stadig attributed the fish’s shorter length to more reliable measuring conditions. “It’s hard to measure a big sturgeon that’s fighting and flopping after it’s netted,” she said. Stadig assures everyone it’s easier to measure sturgeon after they’ve been speared, tagged, loaded into a pickup truck and hauled a few miles to a registration station.
When the DNR caught that fish 11 years ago at Shawano, veteran sturgeon biologist Ron Bruch estimated its age at 125 years. Stadig, meanwhile, estimates it was at least 80 to 90 years old, and no doubt could be “pushing 100.”
“We estimate age based mainly on length and biochemistry that Ron (Bruch) created, and my graph ends at 84 inches,” Stadig said. “When sturgeon grow that big and old, it’s hard to nail down an exact age, even when you collect their pectoral fin and otoliths.”
Pectoral fins lie directly behind the fish’s gill plates on each side. Otoliths, also called “ear bones,” are a pair of coin-sized calcium structures in the head that help fish sense gravity and movement.
Fin bones and otoliths build annual growth rings, much like those grown by trees. Tree rings, however, are easier to count, even with the naked eye.
“A 100-year-old tree has a huge trunk, but otoliths are about the size of a nickel,” Stadig said. During years of high-quality forage, sturgeon grow faster, which muddles the growth rings. Rings are more distinct in slow-growth years. Even with a microscope, it’s hard to count the rings on century-old fish.”
Bruch recalls the excitement at Shawano when his crew caught the old sturgeon in April 2012. He snapped a photo of it, with a dozen biologists and wader-wearing net handlers beaming behind it. “It was definitely the largest sturgeon we ever handled,” said Bruch, who retired from the DNR in January 2015. “She was a memorable fish.”
To help people appreciate the fish’s novelty, Bruch put together a timeline based on historical events. If the fish was the 125 years he estimated, it likely hatched during President Grover Cleveland’s first term in the White House. For history buffs, Cleveland is the nation’s only president to serve two non-consecutive terms, the first from 1885 to 1889, and the second from 1893 to 1897.
But if we go with Stadig’s estimate that the sturgeon was about 100 when speared, you still won’t feel young to learn the fish was born when Woodrow Wilson was in the White House (1913-1921). Even if you go with Stadig’s youngest estimate, the fish was born only months after the U.S. Navy and Marine Corps ended Japan’s occupation of Guadalcanal (January 1943) in World War II.
It’s even more fun to consider how Lake Winnebago’s sturgeon population might look in the decades ahead. These prehistoric fish have benefited the past three decades from better spawning habitat, cleaner water and a richer diet heavy in gizzard shad, an exotic species whose numbers have boomed since the late 1980s. Because of that high-fat diet, healthy female sturgeon now spawn every three years instead of every six. In fact, Bruch documented a female that spawned only two years apart. Likewise, male sturgeon feasting on gizzard shad can spawn every year instead of every other year.
Such feats might look modest if another exotic forage species, the round goby, reaches the Winnebago System. Bruch credits round gobies in Lake Michigan for fattening Green Bay’s rebounding whitefish populations in recent years. He thinks gobies would trigger another boom in sturgeon growth rates should they reach Lake Winnebago by breaching the Neenah dam on the lower Fox River. The agency has already documented round gobies below Neenah.
“Sturgeon love eating gobies, and the older female sturgeon could reach 300 pounds if a big part of their diet is gobies,” Bruch said. “Sturgeon in upstate New York lakes, and around Detroit and Milwaukee in the Great Lakes, are growing faster and spawning earlier because gobies are part of their forage base.”
When Bruch looks at his 2012 photo of the record sturgeon and the jubilant crew that caught her, he points out a lone figure watching from uphill in the picture’s top-left corner. That was Bruch’s predecessor, Dan Folz, or “Father Sturgeon,” the DNR’s legendary biologist who stood 6-foot-7-inches tall. Folz died at age 86 in November 2020 during the COVID-19 pandemic.
So, measured another way, if Folz had laid head-to-head beside that record sturgeon on the Wolf River that day, his boot heels would have been just 6 inches shy of the fish’s tail tip.
That’s assuming, of course, the giant man made the huge fish lie motionless to measure accurately.
This Wisconsin Department of Natural Resources crew netted, weighed and measured this record 240-pound lake sturgeon in April 2012 on the Wolf River below the Shawano Dam. A spearfisherman on Lake Winnebago took it through the ice in February 2019.
— Wisconsin DNR photo by Ron Bruch