Walleye stocking doesn't help at lake
Results of a Youghiogheny Lake survey conducted by the Pennsylvania Fish and Boat Commission indicate the stocking of walleyes has had little effect in bolstering a population traditionally dependent on natural reproduction.
After five years of consistent stocking of both fry- and fingerling-stage walleyes, population levels appear similar to that of pre-stocking years.
Youghiogheny Lake is a 2,840-acre impoundment of the Youghiogheny River that straddles the Pennsylvania-Maryland border. Nearly 80 percent of the lake is in Pennsylvania, forming the Fayette-Somerset county boundary.
A multiuse federal flood control facility, Youghiogheny Lake contains a varied gamefish population that includes walleye. Other species in good numbers are smallmouth bass, largemouth bass and numerous varieties of panfish and baitfish.
Historically, the commission's Youghiogheny Lake management plan has relied on natural reproduction to maintain the walleye population.
"We feel there is successful walleye spawning in the river section feeding the lake and also along the lake shores," said Rick Lorson, the agency's biologist responsible for managing the fisheries in the southwestern portion of the state.
"A number of years ago, there was concern expressed by anglers from that area regarding a problem with walleye reproduction, that there may be missing year classes," he added.
Lorson said Youghiogheny's water chemistry limits the total amount of fish life it can support. The commission uses a measurement of fertility – parts per million of alkalinity — to determine a lake's carrying capacity.
The infertile substrate of the Youghiogheny River valley upstream of the lake limits its ability to buffer the negative impacts of acid mine drainage and acid rain. Though water quality has improved over the past 20 years, the lake's alkalinity level has consistently measured below 20 ppm, the minimum concentration level the agency uses to consider a lake moderately fertile.
In response to public concerns, Lorson said the commission began stocking fry- and fingerling-stage walleyes in Youghiogheny on an annual basis in 2002.
The stocked fish had been chemically marked with oxytetracycline. Though widely used as an antibiotic in humans, OTC also can be used to "tag" fish.
The marking takes place by immersing the fish in an OTC solution in the hatchery before stocking. OTC binds to calcium and magnesium found in fish. In walleyes, this binding occurs on the otolith, the bony structures found directly behind a walleye's brain.
Under microscopic examination, cross-sections of the otolith from successfully marked fish display bright yellow or chartreuse rings.
However, the walleyes stocked in Youghiogheny in recent years were not marked successfully. Lorson said the research on the marking process took place in a soft-water hatchery. The commission's walleye hatcheries at Linesville and Pleasant Mountain both had soft water.
"We learned that in a hard- water environment, the oxytetracycline is not taken into the fish; rather it is bound up in the water," explains Lorson. "The high level of marking we had hoped for did not occur. The amount of information (regarding the percentage of stocked fish in the current population) just didn't happen."
Though managers were not able to determine the role stocking played in the present Youghiogheny walleye populace, he said that given the lake's low fertility, survival of stocked fish might have come at the expense of wild fish.
"There's only room for so many walleye in that water body, regardless of how many go in," Lorson said. "Even if we had the marked fish, it might be difficult to tell the true picture of what's coming out of there.
"But based on what our 2007 trap net survey results, it suggests that stocking has not improved the overall walleye population," he added.
Lorson said last year's survey showed the total walleye abundance as being below its historical average, but not significantly so. When compared to the previous survey, done in 1998, a higher percentage of young year classes, ages 2 through 5, were present in that survey, compared to the work done last year.
Despite signals that walleye stocking will not elevate Youghiogheny's walleye numbers, the commission intends to continue to stock fingerling-stage walleyes at an increased rate for next several years.
Presently, the lake offers plenty for anglers to pursue. At least 96 percent of the 81 walleyes collected in trapnets were legal fish (15 inches or longer); the longest walleye was 25 inches.
And those fish are certainly worth catching, whether they were stocked or not.
