Sturgeon: Special Report (Part 1 of 2)

High above the water, Jennifer Yauck joined one researcher on his weekly hunt for radio-tagged lake sturgeon in the Lake Winnebago system.

It was early morning on a nearly cloudless day this summer when Great Lakes WATER Institute senior scientist Fred Binkowski took to the air in search of lake sturgeon.

As his plane, piloted by Heath Van Handel of the Wisconsin Department of Natural Resources, flew northwest out of Oshkosh, water dominated the view below. To the rear was the 138,000-acre Lake Winnebago; ahead, a chain of smaller lakes-Butte des Morts, Winneconne, and Poygan-that empty into Winnebago after being fed by the Wolf River from the north and the Fox River from the south. He has been flying over these connected waters-collectively called the Lake Winnebago system-almost weekly since releasing 12 juvenile sturgeon on the west end of Lake Poygan in April 2007.

Wisconsin’s largest and longest-lived fish, the sturgeon has been around since the time of the dinosaurs. The fish was once plentiful in the Great Lakes and inland waters, but its population in many places dwindled in the past century due to overharvesting, pollution, and habitat degradation. However, thanks to management and research, the Winnebago system today is home to an estimated 40,000 adult sturgeon, the largest such population in North America.

The fish Binkowski released into the system were raised from eggs in his lab. Each bears a radio transmitter that sends out a unique signal, heard as a “beep” through a special receiver. The technology allows Binkowski to track the movements of individual fish from the sky, and learn more about sturgeon as a whole. His data will inform efforts to both restore the ancient fish to its original waters and maintain the viability of the Winnebago system’s already thriving population.

Click photo to enlarge.

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Near the imaginary line separating lakes Winneconne and Poygan, Binkowski easily picked up the first fish’s signal. “Mark it,” he told Van Handel, who recorded the plane’s position on a GPS unit. He located another sturgeon several minutes later.

But the next two fish, last detected on the west side of Poygan, were harder to pinpoint, emitting only faint beeps. Perhaps the fish were beneath rocks or in a deep hole. For the next half hour, the plane flew a grid pattern over the water until Binkowski finally got a clear read on each of the elusive fish.

Binkowski has radio tagged over 100 sturgeon since he began using the technique in the early 1990s. He’s noticed that among the juvenile fish released into the Winnebago system, a striking number-about half-eventually settled into Poygan. Some of his currently tagged fish have never left Poygan at all.

“That’s telling us Poygan is very special in terms of habitat and food,” said Binkowski. “There’s something there that’s of real value to these fish.”

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The plane was headed north up the 125-mile undammed stretch of the Wolf River in search of the day’s last sturgeon when Binkowski again heard a weak signal. “We might have to do a treetop on this one,” he told Van Handel. Quickly, the pilot circled the aircraft back around, dropping low to the brown river and its thickly wooded banks. He steered the plane upstream for a second pass, banked left and then right to match two of the winding Wolf’s curves, and then throttled skyward just in time to clear rapidly approaching trees.

“I got three beeps,” said Binkowski. “It’s just upstream from the bridge.”

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Every spring, the sturgeon already residing in the Wolf are joined by many others from the Winnebago system that migrate upriver seeking rocky habitat and fast-flowing water for spawning. Males reach sexual maturity at about age 15, with individuals typically spawning every other year. Females mature at about age 25 and spawn every three to four years.

Distracted by their mission to mate, spawning adult fish are fairly easy to capture for assessment, and are therefore the source for most of the knowledge researchers have about sturgeon. Considerably less is known about young fish. Binkowski hopes his radio-tagging studies will help fill this gap. Click to enlarge photo

This fall, Binkowski will tag several wild sturgeon in the Wolf to compare their movements with his captive-born fish. In spring, he plans to release more young tagged sturgeon into Poygan to confirm his earlier finding that the fish have a preference for the lake. “If we get similar results, that opens up a whole new book on sturgeon life history and movement,” he said.

Eventually, he will also investigate the sites frequented by the fish in order to determine the types of food and habitat they offer. “Today, at least for a percentage of these fish, we know where they’re at, and when they’re there,” he said. “Eventually we’re going to nail it down to why they’re there, too.”

Part 2 of this series will explore the history of sturgeon research and management in Wisconsin.

Jennifer Yauck is a science writer at the Great Lakes WATER Institute. GLWI (glwi.uwm.edu) is the largest academic freshwater research facility on the Great Lakes.

A STURGEON NAMED PORKCHOP

Among the lake sturgeon raised from eggs at the WATER Institute, perhaps none is better known than Porkchop.

Born in 1983, the male fish grew to a weight of about 70 pounds and a length of about five feet.

According to scientist Fred Binkowski, Porkchop earned his nickname because of his fondness for his tank’s automatic feeder. “He knew where the food supply was and would just wait there for the timer to go off,” said Binkowski.

Porkchop’s tank was a favorite stop for many visitors to the WATER Institute. The fish also was a model for researchers as they studied hormones and tested a passive tracking device called a sonic tag on him.

Earlier this year, researchers released the 25-year-old Porkchop into the Montello River. According to data gathered from sonic monitoring stations positioned at various points along that water system, Porkchop moved into the Fox River, and eventually ended up somewhere in Lake Puckaway, where it appears he has stayed since, likely dining on snails, insects, and other small organisms. “It’s a fairly shallow lake and it’s like a buffet table for him,” joked Binkowski. “Why would he leave?”

~Jennifer Yauck

Click images to enlarge.