DNR biologist works to restore walleye
ATHENS, Ohio -- Someday, when West Virginians catch really big walleyes, they'll have a woman working alone in a science lab to thank.
Her name is Katie Zipfel. Without her, fish hatchery workers wouldn't be able to tell one walleye from another -- and state fisheries officials wouldn't be on track to restore several Mountain State trophy walleye fisheries to their past glory.
Zipfel, a Division of Natural Resources fisheries biologist, is the agency's resident expert on walleye genetics. With some scientific sleight-of-hand and a dash of laboratory legerdemain, she can tell a Lake Erie fish from a native West Virginia fish.
"We look for genetic 'markers' that are unique to different strains of walleye," she explained. "Those markers allow us to tell one strain from another. The process involves five separate steps, and they all take time. Sometimes it feels like I'm pipetteing my days away, but I absolutely love it."
Zipfel's work is important because DNR officials want to gradually get rid of Erie-strain walleyes and replace them with homegrown native stock.
Half a century ago, West Virginia had some serious trophy walleye waters. The New and Elk rivers routinely produced 10- to 15-pound fish -- not huge numbers of them, but enough to make those waters must-fish destinations for serious walleye anglers.
After walleye populations declined in the 1960s and 70s, DNR administrators began importing and stocking juvenile Erie-strain fish from Pennsylvania's Pymatuning Lake and New York's Lake Chautauqua. The stockings boosted populations somewhat, but never really lived up to officials' expectations.
Biologists found out why in the early 2000s, when fisheries researchers at Virginia Tech discovered that some walleyes in the New River watershed had distinct genetic characteristics.
"They found that walleyes running upstream from Claytor Lake went to different riffle areas to spawn," Zipfel said. "They did genetic workups to try to understand why some fish went to some riffles while other fish went to different riffles. They found that there were significant genetic differences between the two strains."
All of a sudden, West Virginia officials understood why the Erie fish hadn't prospered or grown as large as those trophy walleyes of yesteryear: Erie-strain fish weren't genetically programmed to thrive in Mountain State rivers, while native-strain walleyes were.
DNR officials soon realized that if they phased out Erie-strain stockings and started growing native-strain fish in state hatcheries, they might be able to reconstruct self-sustaining walleye populations in rivers that once harbored them.
The trick was to figure out which walleyes were foreigners and which were natives. Enter Zipfel, who had done her master's thesis on walleye genetics. Her advisor, Dr. Matt White at Ohio University, had developed a process for finding the unique DNA "footprints" that distinguish one strain of fish from another.
That process keeps Zipfel busy. Three times a year, she commutes from her Parkersburg office to the OU genetics lab and spends a couple of weeks analyzing walleye tissue samples.
"The samples are from fish that our crews capture to serve as brood stock," Zipfel explained. "Every walleye we capture gets tagged so it can be identified, and has part of one fin clipped off for tissue analysis."
Since DNR officials want to raise only native-strain fish, they need to know which captured walleyes are natives and which are from Erie stock. They send the clipped fins to Zipfel for analysis.
"I run the samples 'blind' so I don't bias myself," she said. "The first thing I do is to extract and purify the DNA, which puts it in a liquid form. After that, I take it and run a polymerase chain reaction, which allows me to make an ungodly number of copies of a single piece of DNA."
She then places the tiny DNA samples -- it would take a million of them to fill a liter-sized water bottle -- into separate tubes, each containing a different protein.
"One protein cuts the DNA of a native walleye in half, the other cuts the DNA of a Lake Erie walleye in half. One gives a positive and one gives a negative," Zipfel explained.
To further clarify her findings, Zipfel takes all the native-strain samples and performs what she calls a "microsatellite analysis" of their nuclear DNA.
"At that level, we're looking for two to five base pairs that repeat at certain locations within the DNA strand. We look at two different locations, and we count the number of repeats at each location.
"We're looking for very specific numbers, which were developed when the Virginia Tech folks first isolated the native strain. When we find those numbers, we know we have a native walleye."
When Zipfel determines which of the captured walleyes are native, she relays her findings to hatchery officials, who use the natives for river-bound brood stock and save the Erie fish for lake-dwelling populations.
She also analyzes tissue samples from walleyes taken during routine fishery-health surveys.
"We do that to see if our native-strain stockings are helping us to get closer to a population in which natives are dominant. We check from year to year to see if the percentage of walleyes with native markers has increased," she said.
Zipfel joked that she might one day develop carpal tunnel syndrome from all the pipette work she does in the lab. She added, however, that the work is worthwhile.
"I get a thrill every time I find a native-strain fish," she said. "When one pops up, it's like, 'Yes!'"
Though she hopes one day that her work will resurrect a once-thriving trophy walleye fishery, Zipfel said she takes even more satisfaction that she's helping to preserve a small slice of West Virginia's biological heritage.
"I got into biology because I wanted to save the cheetahs," she said. "Well, I ended up in fisheries. But the work I'm doing has the same goal -- to attempt to conserve a unique bit of nature."
Reach John McCoy at firstname.lastname@example.org or 304-348-1231.