ST. GEORGE — If you’ve done any fishing lately at any of the community fishing ponds and even some local reservoirs, chances are you may have seen or even caught an invasive fish. Vibrantly colorful and surprisingly large koi are unmistakable in Baker or Ivins Reservoir, while smallmouth bass continue to frustrate wildlife officials as they try to monopolize Quail Creek Reservoir.
According to the Utah Division of Wildlife Resources, nearly all community fisheries in the St. George area now host colonies of koi fish. Southern Region Aquatic Program Manager Richard Hepworth said these fish are usually introduced by families and individuals dumping their unwanted pets in the nearest pond or waterway.
“Koi are not very desirable for table fare, and they compete with species like rainbow trout that people tell us they want to catch,” Hepworth said. “Smallmouth are a very direct threat to the native species within the Virgin River system. If they got out into the river system, not only would they compete, but more likely they would prey on and eat these native species that we’re trying to keep from being endangered. ”
In 2015, the population of smallmouth bass at Gunlock Reservoir got so out of control that the Division of Wildlife Resources treated the entire reservoir with rotenone. In the years following, Kolob Reservoir also received a similar treatment to deal with its runaway invasive species problem.
This powerful piscicide, which is formulated to shut down a fish’s gill function, is usually reserved as a last-ditch effort since it will kill any and all fish in the treatment area. Each process costs about $30,000, and Baker Reservoir may soon require its own rotenone treatment, Hepworth said.
“We try to do removal efforts,” Hepworth said. “If you catch a smallmouth bass in Quail Creek, it’s against the law to let that go: you have to kill that fish. With these koi in community fisheries, such as Ivins, I’d encourage them (fishermen) to kill those fish.”
However, Hepworth said that the koi reproduce so quickly that even community removal programs will not be enough to reduce the population, and the invasive koi will ultimately have to be removed by other methods.
Managing the fisheries is the responsibility of the Division of Wildlife Resources, but other contributing agencies include the Virgin River Program, the Washington County Water Conservancy District and the U.S. Fish and Wildlife Service.
Kelly Giacomazza, a Washington County resident who fishes at Ivins Reservoir almost daily, said that he isn’t troubled much by koi since they don’t tend to bite with the bait he uses.
“Personally, I don’t mind the koi fish because they’re cool looking,” Giacomazza said. “I was surprised to see how many there are here. There’s a lot: red ones, orange ones, yellow ones, white ones and even some that are spotted like dalmations.”
Though he rarely catches them himself, he said he’s seen other fishermen haul in koi as heavy as 15 pounds.
“That type of fish – koi fish or carp – to the rest of the world that’s a sport fish,” Giacomazza said. “Here it’s considered a trash fish. They’re fun to catch because they fight hard and they’re strong.”
For Hepworth and the Division of Wildlife Resources, koi and smallmouth bass are especially problematic because they compete directly with sport fish that the agency stocks, specifically rainbow trout, bluegill and largemouth bass.
“Sometimes it’s more about compatibility and sometimes it’s more about desirability, Hepworth said. ”It all comes down to doing our very best to manage not just a specific pond or a lake, but a greater ecosystem for multiple different species and multiple uses. When you start introducing new species, they can mess with that whole ecosystem.”
Ultimately, none of these removal efforts will be truly successful until people stop ditching their fish, Hepworth said.
“It is against the law to release a pet into a pond or lake in the wild,” Hepworth said. “You’re doing a lot of damage. We don’t necessarily want to give people tickets or citations, we just want the people not to do it. That’s the bottom line.”
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