JEFF KNAPP: PFBC assesses walleye stockings
Pennsylvania Fish and Boat Commission assessments of the Allegheny River’s walleye fishery conducted over the last six years have provided insight regarding natural reproduction, the level at which river-bred fish have survived to become adults, and also the significance of a native river-strain walleye.
As part of its current walleye management plan, supplemental stockings of walleye in the Allegheny were discontinued in 2007 to determine if natural reproduction was adequate to maintain a high-quality fishery. Prior to this, stockings of fry and fingerling-stage walleyes occurred regularly from the Kinzua Dam tailrace downriver to Lock and Dam 6 near Clinton. Stockings downstream of Lock and Dam 6 were relatively rare, with four plantings that occurred in 1976, 1977, 1980 and 1983. All were in the extreme lower end of the Allegheny between the Monongahela River confluence and the Highland Park Dam.
For the past six years the Fish and Boat Commission has evaluated the Allegheny’s walleye population at nine sites, six in the free-flowing portion and three in the impounded lower section. The upper sites are the Kinzua tailwaters, Starbrick, Tidioute, Tionesta, President and Oil City; lower sites were East Brady, Templeton and Freeport.
The annual fall assessments were targeted at young-of-year walleyes (less than 9 inches); adult walleyes were also collected. The method of collection was nighttime electrofishing, with the numbers of fish collected per hour of effort being the gauge used in the evaluation. Catch rates of YOY walleyes captured at 20 per hour, and legal walleyes (15 inches or longer) at two per-hour, were the targeted goals, levels the agency has determined translate into a quality fishery for anglers.
“The young-of-year catch results are thought-provoking,” said PFBC Three Rivers Fisheries Biologist Bob Ventorini. “Over a six-year period, President and Freeport only met the target catch rate once, while Tidioute was the least productive, not meeting our walleye plan objective in any surveyed year. Kinzua did not perform that well, either, over four years of surveys. On the other hand, Oil City met or exceeded the target catch rate half of the time, while Templeton performed the best of the sites surveyed — meeting or exceeding our expectations for young-of-year walleye for all six years.”
Ventorini also noted that the most productive year for natural reproduction of walleye (within the past six years) in the Allegheny River appeared to be 2010. Fluctuations in hatch success from year to year are common in rivers, influenced by factors such as weather, water levels, predation, food sources for fry and availability of spawning habitat.
However, low young-of-year catch rates haven’t translated into low numbers of legal walleyes. For instance, Tidioute and Kinzua produced a high level of legal fish, averaging four to five times the two-fish-per-hour rate during the survey period.
Ventorini said it’s likely that differences in habitat within the survey areas impacts the numbers of fish collected, factors such as available shallow water cover and access to deep water. For instance, young-of-year walleyes were collected in good numbers at Oil City and Templeton, where a narrow fringe of weeds gives way to deep water, indicating perhaps that the young fish were concentrated in the available cover. Legal walleyes showed up in much higher numbers at upper Allegheny River sites such as Tidioute and Kinzua tailwaters, where the survey site is comparatively shallow, and the fish more susceptible to being stunned by the shock of the electrofishing gear than at other sites, such as the three in the impounded river section.
A highlight of the 2013 work also produced several trophy-sized walleyes, including the two biggest ever collected during Allegheny River surveys, which weighed 12 pounds, 10 ounces and 12 pounds, 8 ounces.
In addition to valuable information regarding natural reproduction — and how that is translating into adult fish for anglers — the 2013 survey will also provide important data relative to the “Highlands” walleye strain, one native to the Ohio River drainage. Ventorini cited work being done by Matt White, Ph.D., a biology professor at Ohio University in Athens. The Highlands strain is a river fish, unlike the Lake Erie walleye strain. Walleye brood stock in Pennsylvania come from the Lake Erie strain, hatched and reared primarily at the commission’s Linesville hatchery, and are adapted to lake environments.
“Dr. White and his colleagues at Ohio University have revealed two different lineages,” Ventorini noted. “Characteristic differences were found between the genetically distinct and widely stocked Lake Erie walleye strain and native Highlands walleye strain — named after a strain found in the Ohio River, the New and Kanawha rivers in West Virginia and the Cumberland River in Kentucky. Their goal has been to determine the distribution of the native Highlands strain and to identify those populations of natives that appear to have avoided hybridization with the introduced Lake Erie strain.”
Ventorini said PFBC personnel clipped fin samples of 155 walleyes collected at various sites during the 2013 field work. These samples were sent to Ohio University, adding that at this point about half have of them have done. All of these samples have turned out to be Highlands River stain.
With six years of research now complete, Ventorini expects the agency to make a decision within the next several months on whether to continue suspension of walleye stocking on the Allegheny. He thinks the agency should continue to monitor the river’s walleye population, perhaps with a reduction in the number of survey sites. He’d also like to see a November survey where adult walleyes are targeted.
“Hopefully the decision to stock or not stock will be made based on a consensus of a group of biologists, and not just one person,” Ventorini said. “My opinion is that the data support not stocking walleye. My opinion will grow stronger if we find out that all or most of the fin clips we provided Dr. White were collected from Highlands strain walleye.”