Glaciers and biological chance set apart the walleye that angler Cecil Murray seeks in the lower Current River’s deep pools. A particular strain of this toothy fish swims only in four southeast Missouri Ozark rivers. Its closest genetic relatives live far away in a few streams in western Appalachia. It has typical walleye golden-green colors and eyes that appear glassy when held at certain angles. But MDC geneticists, fish hatchery managers, and fisheries biologists know from lab tests and field experience that this fish is different from most other walleye strains in North America.
For a quarter century, MDC staff has worked to save distinct genetic traits the Black River-strain walleye carry in the Current, Black, Eleven Point, and St. Francis rivers. Genetic diversity in nature provides strength and beauty. Anglers benefit from the genetics in this fish because the Black River-strain grows larger than walleye strains native to northern states, and they’re catchable from the ever-flowing beauty of a river.
“Walleye down here are considered the best eating fish in the river,” said Murray, 78, of Doniphan. “They’re a lot of fun to catch on top of that.”
Whether from wooden johnboats or modern jet boats, Murray has fished for walleye in the Current River all his life. He’s guided anglers on the river since he was 18. Walleye start biting his trolled crankbaits in late August, and he catches them through winter and the early spring spawning run.
“The biggest walleye I ever saw was a 17-pounder.” Murray said it was a fish caught by another angler.
But the river’s fishery got even better for anglers two decades ago when MDC began stocking Black River-strain fingerlings raised in a hatchery.
“We didn’t use to catch as many walleye as we do now,” Murray said. “I’d have to say for sure it helps.”
Fishy Genetic Surprise
Anglers historically caught walleye from rivers throughout the state, but rarely in large numbers. Missouri is on the southern edge of the species’ native range. When some rivers were dammed to create lakes, new walleye habitat was created, and MDC raised walleye in hatcheries to supplement their numbers. That approach has supported a popular and productive walleye fishery in lakes.
Early in stocking programs, brood fish often came from the Great Lakes region. Managers stocked Northern fingerlings and fry under the assumption that a walleye is a walleye, no matter its origin.
But fisheries biologists also wondered about the surprisingly large walleye caught from lower reaches of rivers like the Current and the Black. A 20-pound, 8-ounce walleye caught from the St. Francis river in 1961 held the state record until 1988. Although river walleye populations weren’t large, anglers often caught big ones, especially during spawning runs in late winter or early spring. Large fish and river settings make them special, said David Knuth, MDC fisheries management biologist. Anglers have a chance to catch a 14- or 15-pound walleye, or bigger.
“For anglers, where else can you go fish in a clearwater river for a walleye that’s a wall-hanger?” Knuth said.
MDC biologists in the 1960s wondered if more wall-worthy walleye could be provided in those rivers by stocking hatchery-reared fish. A study of river walleye was followed
by an experimental stocking in 1969 of Great Lakes-strain hatchery fry in the Current River. The fry didn’t survive well enough to increase the population. That was a clue river walleye are different from lake-origin walleye.
In the 1990s, genetic science revealed just how different they are. MDC and fisheries biologists around the nation began to recognize the importance of genetic diversity in all fish species strains, and new lab technologies enabled them to track genetics. MDC embraced new scientific discoveries and implemented a fisheries policy to preserve local genetic stock whenever possible.
In the late 1990s, MDC prepared to restore walleye to the upper St. Francis River with brood fish from the Black River, an adjacent basin. Jeff Koppleman, a former MDC fisheries researcher, tested the DNA of walleye from around Missouri. He discovered that walleye from the Black and Current rivers had genetics distinct from those where lakes had been stocked with hatchery fish with origins in the Great Lakes region.
“Jeff caught a glimpse of something special, and it’s resulted in something even more special,” said Leah Berkman, MDC biometrician and geneticist.
In 2017, Berkman used DNA sequences from Koppleman’s research and the same genetic data from studies in other states to connect the Missouri fish with unique but similar walleye strains in a few western Appalachian streams in West Virginia, Kentucky, and Ohio. That revealed the relationships between the southeast Missouri walleye with what fisheries biologists nationally call the Eastern Highlands walleye strains, distinct from walleye labeled as Great Lakes strains.
“It’s just a really clear, obvious thing from a genetic standpoint,” Berkman said. “Some things are not as nice and clear as this.”
Biologists looked to ancient North American glaciers for answers why. A leading theory is that a great, preglacial river called the Teays once flowed northwest from the Appalachian Mountains and then west to join an ancient Mississippi River course, waters mingling within fish-swimming distance of where Ozark rivers met the Mississippi. But advancing and retreating glaciers during the Pleistocene geologic epoch altered the rivers’ courses, buried valleys, created new rivers, and cut off walleye populations in Teays River courses from similar walleye in the Ozarks. Walleye where the Black Riverstrains are found today were also cut off from walleye in other Missouri streams.
“They’ve got a great back story from the glaciers,” said Berkman, who is a fan of the fishes’ uniqueness. “And I don’t fish,” she said. “I’m a data nerd.” Help From Hatcheries
In 1998, MDC implemented a statewide walleye management plan that included stocking only the Black River-strain in the Current, Black, Eleven Point, and St. Francis rivers to keep those fisheries healthy. But raising the Black River-strain in a hatchery has proved to be more difficult than raising Great Lakes strains. Genetics are not the only difference between river and lake walleye.
The adults look identical, but the river-strain eggs are up to 25 percent larger. Fry, once hatched, need to be moved more quickly to rearing ponds to feed. Plus, nature and the weather don’t always match up well with hatchery schedules.
This year, heavy rains in February brought high water and flooding just when MDC fisheries biologists were attempting to collect brood stock from the Black and Current rivers. They use nets and electroshocking to collect females and males preparing to spawn in February and early March. Often, they work at night when walleye are active and moving upstream, dealing in some places with swift river currents and rocky shoals. The Black River walleye “are the earliest in the state for spawning,” Knuth said. Females are often done by the last week of February.
On March 4 of this spring, biologists collected the last group of brood stock fish needed for 2018’s hatchery spawning, four females and 20 males from the lower Current River. The biologists attached a slender plastic ID tag on each fish, so they can be tracked through the hatchery process. Andy Cornforth, manager of MDC’s Chesapeake Fish Hatchery near Mount Vernon, drove over that night to pick them up. The hatchery staff began preparing the fish for spawning the next day. Each walleye was weighed, measured, and given hormone shots to enhance the spawning process before it was placed in holding tanks.
Egg samples were pulled to examine how close the females were to spawning. Most females weighed 4 to 6 pounds, but they can be bigger.
“The biggest females we’ve had in here have weighed 16 to 18 pounds,” Cornforth said.
Samples from fins were also clipped and shipped to MDC’s Conservation genetics lab in Columbia. Berkman and staff do DNA analysis for each fish before it is spawned at the hatchery to ensure it is a Black River-strain walleye.
When the females are ready to lay eggs, hatchery staff strips the eggs and fertilizes them with milt extracted from the males. Staff then place the eggs in jars with water flowing through them until the fry hatch. When the fry are three days old, staff move them to outdoor rearing ponds that have been fertilized to encourage phytoplankton and zooplankton growth.
“They have to get on food pretty quickly,” said Brad Russell, assistant hatchery manager. “They start eating the zooplankton out in the pond.”
In the river, the walleye females will lay eggs when they are ready, males will fertilize the eggs with milt, and then the eggs and fry must survive predators and the stream’s variable currents. Each adult fish is a miracle, considering all they must survive.
Conditions at the Chesapeake Hatchery are more controlled but not foolproof. The fry do best when water temperatures in the rearing ponds are above 50 degrees, but that’s springweather dependent. In 2017, an extreme temperature drop chilled the water in rearing ponds and wiped out the year’s hatch of walleye fry.
Hatchery staff this year ended up with 370,105 Black River-strain fry out of more than 1.2 million eggs fertilized, Cornforth said. They then stocked 151,000 fry in three rearing ponds. The remaining fry were shared with Arkansas, which is cooperating with MDC on management of the strain in shared waters. Over the last 20 years, the hatchery has averaged an 11-percent return of Black River-strain fry reaching the fingerling stage for stocking, Cornforth said. The Great Lakes strains average 50 to 55 percent return in a hatchery.
Black River-strain propagation owes much of its success to the hatchery staff working through unusual challenges. This year’s cold spring took a toll on fingerling numbers.
“It’s a very finicky fish, even though it looks like any other walleye,” said John Ackerson, MDC fisheries management biologist.
In May, MDC biologists stocked 20,000 Black River-strain fingerlings an inch or more long into the lower Eleven Point River. The fingerlings were offspring of 10 females and 27 males handled by the hatchery this spring. Carefully, the fingerlings
are moved from trucks to the river via boat, into deep pools where the current and predators are minimal.
“There’s a lot of time and effort that goes into raising these guys, so we want to give them the best chance for survival,” said Blake Stephens, an MDC fisheries management biologist supervising the stocking.
MDC includes 148 miles of the four Ozark rivers within the Black River-strain management program. Each river is stocked once every four years in a rotation. The approach helps preserve the Black River-strain’s unique genetics and serves anglers. “We’re increasing the year-class strength for anglers,” said Paul Cieslewicz, an MDC fisheries management biologist who has worked on the river walleye program since its inception. “In three years after stocking, we’ll have a big year-class of 16-inch fish.”
Data and observations about fingerling stockings and fish movement suggest the Black River-strain possesses adaptations that enhance their survival.
“My feeling is these fish are suited for the river system,” Cieslewicz said. “They have some kind of advantage, though I can’t tell you what it is.”
Berkman will continue to do DNA analysis on walleye from various streams and lakes in Missouri and Arkansas, looking for more fish with surviving native genetic traits. She admires the MDC fisheries biologists who decades ago chose a policy that preserved the Black River-strain’s uniqueness.
“They were thinking about this early and choosing not to take the easy route,” she said.
Their dedication to science has also helped anglers like Murray.
“My dad and his dad, and local people, they all fished this river,” Murray said of the lower Current. “But I guarantee you that we catch more walleye now than we used to.”