DILLON — Shrimp, apparently, are smarter than they look. Or at least they’re smarter than the trout in Dillon Reservoir.

While scientists may be hesitant to credit Colorado’s freshwater shrimp population, Mysis diluviana, with anything resembling genuine intellect, there’s no denying that the tiny crustaceans originally introduced to fatten up fish have an aptitude for survival. Meanwhile, it’s the trout and salmon they were supposed to feed that are suffering.

“Mysis are really cold-adapted. They prefer temperatures below 50 degrees,” said Brett Johnson, a fisheries biology professor at Colorado State University’s Warner College of Natural Resources. “The original idea when they were stocked in Dillon Reservoir was to enhance fish growth, but they are actually competing with fish for food by coming to the surface at night as a strategy to avoid predation. They’ve adapted to stay in the cold water at the bottom of the lake by day and come up to feed on the zooplankton at night. Fish, at least most fish, haven’t figured that out.”

Johnson heads up a team of researchers focused on studying the ecosystem and ideally fixing the long-standing issues with the cold-water fishery at Dillon Reservoir. The key to correcting the mysis shrimp mistake and finally establishing the 50-year-old Summit County impoundment as a reliable destination fishery, they say, may ultimately come from another outsider known as the Arctic char.

“Char and mysis both evolved in the same region, the Arctic,” Johnson said. “We got excited to look at Arctic char as an answer to the mysis issue because they are known to eat them, and it’s kind of a special fish. It’s really quite spectacular in its breeding coloration, a hard fighter and a great eating fish. So it’s got the qualities that anglers want. On top of that, it’s able to make use of the biomass that’s short-circuiting the energy flow through the food chain.”

Colorado Parks and Wildlife began stocking the equally cold-adapted Arctic char as a way to combat Dillon’s mysis population back in 1990, establishing the lake owned by Denver Water as the only public fishery in the lower 48 states west of Maine where the fish are found. By default, the state-record char measuring 20.5 inches and 3 pounds, 12 ounces, was landed by Marshall Brenner here in 1994. Researchers have subsequently caught two larger fish.

Stocking efforts have continued on and off through the years, with evidence of a naturally reproducing population as well. But while Dillon Reservoir’s char population is estimated in the thousands, its mysis population is measured in the billions.

“It wasn’t surprising but a little disappointing that the current char population is eating just a tiny percentage of mysis that are out there,” Johnson said after building bioenergetics models to map the flow of calories through the food chain. “There’s not going to be an impact unless the population is built way up.”

Perhaps the only other fish suited to the task are lake trout, or mackinaw, a notoriously ravenous species that has been known to take a toll on other sport-fish populations. Once growing lake trout graduate from mysis, they move on to eat brown and rainbow trout, kokanee salmon and even char, Johnson said, adding that their introduction to the lake sitting at 9,000 feet would be a “tragic mistake.”

After three years of study, Johnson’s research team, which also includes CSU fishery biology master’s student Devin Olsen, CPW biologist Jon Ewert and lifelong scientist and financier Douglas Silver, remains hesitant to recommend a committed stocking effort of Arctic char for the foreseeable future, although the notion holds promise. Beyond the risk of unintended consequences, the obvious hurdle is the cost of raising enough char in the hatchery to put a dent in the mysis shrimp population that has thrived since its introduction to the lake in 1970.

Supporters believe that a portion of that expense may be recouped by changing Dillon Reservoir’s reputation from that of an underwhelming trout fishery to a unique sport-fishing destination capable of increased contribution to fishing’s $1.3 billion annual impact on the Colorado economy.

“You can catch trout anywhere in Colorado, so we want to focus on a unique fish in the state,” Silver said. “Now that we’ve jumped off on char, can we make Dillon into a boutique fishery, a place that brings people to Colorado? We’re hoping that char can make Dillon into the destination fishery it deserves to be.”