"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 johnmc...@wvgazette.com or 304-348-1231.