Like so many of life’s mysteries, the riddle of walleye fishing in Chatfield Reservoir, as well as around Colorado, can be solved by science.
Colorado Parks and Wildlife biologists recently wrapped up the annual spring egg-taking ritual used to populate Colorado reservoirs with the popular game fish. And the early indications of increased size and volume of fish in Chatfield should be music to anglers’ ears.
Walleye populations plummeted in the southwest suburban impoundment after a furious spring runoff in 2007 dumped a significant portion of the fish through the dam and into the South Platte River below. While some fish are lost in the flood every year, the abrupt flush 5 years ago carried away far more than normal.
“The number of fish we caught in 2008 compared to a normal year — say, 2006 — I’d say we lost two-thirds of the adult population fish 3 years old or more,” said Paul Winkle, CPW aquatic biologist for the metro area.
“It really decimated the walleye population,” added Ken Kehmeier, a senior biologist out of Fort Collins. “But the thing I think is real important is that we’re starting to see the results of our stocking from that 2007 year class now because they’re 4-5 years old.”
For the past three weeks, Kehmeier, Winkle and a team of CPW biologists have been dropping nets at strategic locations in Chatfield, Cherry Creek and Pueblo reservoirs in order to collect walleye eggs for rearing in state hatcheries. After handling hundreds of fish a day, some 96 million eggs are stripped and mixed with milt in the hatcheries before about 3 million quarter-inch fry are placed in Chatfield Reservoir alone. Natural mortality claims the vast majority of the fry, leaving an estimated one-half to 1 percent to survive their first winter.
And while a hardy runoff can take many of the larger fish with it, the aggressive stocking program is a remedy for long-term concerns.
“That’s why walleyes lay so many eggs, because the odds of them surviving are not great,” Winkle said. “The brood lakes like Chatfield, Cherry Creek and Pueblo, where we want to increase the odds of getting a good year class, we’ll also stock some fingerling walleyes at about 1¼ inches. For instance, I think here at Chatfield we might stock about 14,000 of those 1¼-inch fish. So they’re bigger, and their chance of surviving is higher.”
The stocking story is the same in most of Colorado’s walleye fisheries. Only Horsetooth Reservoir and Carter Reservoir are capable of sustaining naturally reproducing walleye populations in Colorado, although stocked populations have been maintained within state borders since walleye were first introduced to Bonny Reservoir about 50 years ago.
For years, the impoundment along the Republican River alone maintained Colorado’s walleye population, spreading south to Pueblo and eventually to Chatfield and Cherry Creek as demand for the tasty fish rose and water quality deteriorated at Bonny.
“Historically, the big name for walleye fishing has been Pueblo, just because it’s such a big body of water,” Kehmeier said. “But we did a creel survey at Jumbo Reservoir last year, and that was probably the best walleye fishery in the state last year. Good water, lots of fish, they were growing good and the forage base was there.”
Typically, the challenge to growing big walleye in Colorado comes down to maintaining a forage base, primarily gizzard shad. Fluctuating lake levels due to irrigation and municipal needs at many reservoirs can combine with cold winters to kill off shad and subsequently shrink the size of predatory walleye.
“But Cherry Creek and Chatfield are nice because they don’t fluctuate very much,” Kehmeier said. “That’s ideal for both the gizzard shad and the walleye because you don’t see these big evacuations in water.”
That scenario has potential to change in the near future at Chatfield, should a pending reallocation project expand the size of the reservoir by an additional 12 vertical feet of water storage for various municipalities along the Front Range. Increased demands for water are likely to impact storage levels on the reservoir originally established for flood control.
“I think it’s possible to do it right, to mitigate it where we can maintain the walleye fishery and enhance the river downstream,” Kehmeier said. “But we really have to work out the operations of that project. It will take a partnership.”
Meanwhile, the little fish are growing up in Chatfield, with adults currently averaging about 3 pounds and 16-17 inches long. That’s a little smaller than the fish netted at Cherry Creek Reservoir, Kehmeier said. Biologists hauled up about three times as many adult walleyes on a given day than they did at Chatfield. Smallmouth bass still outnumber walleye at Chatfield by more than 2-to-1.
“The fun part about what we’re seeing at Chatfield is that we foresee in the future that we’ll be handling 5-pound, 6-pound fish that will be giving us more eggs in a shorter time period,” Kehmeier said. “That means good fishing, but also, even though we love doing this, doing it for three weeks in a row is kind of like having peas every day for lunch.”
Soon enough, they should be eating walleye.
