KOLOB RESERVOIR, Washington County — Utah Division of Wildlife Resources officials have to kill and restock the fish in a reservoir for the third time in a month after another fish species was illegally introduced.
Kolob Reservoir will temporarily close from Oct. 14 to Nov. 1 for a rotenone treatment, a chemical that is commonly used for killing off fish when invasive species are released into reservoirs and lakes and disrupt the ecosystem, according to a Utah Division of Wildlife Resources news release. After all the fish are killed off, they are removed from the water and wildlife officials can restock healthy fish to grow and repopulate the body of water.
Rotenone is only threatening to the fish, not to people, pets or wildlife.
Kolob Reservoir is typically known for its supply of cutthroat, brook and rainbow trout, according to the DWR website. But this summer, biologists found invasive species of bluegill, yellow perch and green sunfish in the reservoir, wildlife officials said in a news release. The invasive species prey on and compete with the trout for food, resulting in smaller fish sizes and a decreased population.
A $3,000 reward is being offered for information that leads to the conviction of the person who illegally introduced the fish into Kolob Reservoir, wildlife officials said. If convicted, the person may have to pay for the cost of treating the reservoir, which is estimated to be between $15,000- $20,000 according to DWR officials.
Drought has caused water levels at Kolob Reservoir to drop so it is good timing for further lowering the water levels and then doing the treatment, officials said. The water levels are currently so low that boats can no longer be launched into the reservoir, according to the DWR website. Wildlife officials said they will keep water levels low for the rotenone treatment so they can more easily gather the dead fish.
For anglers, the daily trout catch limit has been raised to eight and bait fishing has been allowed until the treatment begins. Wildlife officials are encouraging people to catch and keep more fish since they will be killed off by the treatment soon.
In 2015, a rotenone treatment was done in Gunlock Reservoir in Washington County and proved successful, which was one factor that led to the decision to treat Kolob Reservoir, officials said.
“Today, Gunlock is recovering," the DWR news release stated. "It’s currently a thriving sport fishery for largemouth bass, bluegill sunfish and black crappie.”
This is the third body of water in Utah being closed due to a rotenone treatment in October. Pelican and Maple Lake are also being treated and closed after an infestation of common carp and goldfish, respectively.