Goldfish have taken over a Utah lake — and state officials are fighting back

(Utah Division of Wildlife Resources) A goldfish

At first, anglers thought the fish were kind of neat. A flashy, albeit infrequent, anomaly attached to the end of their fishing lines, a small orange snag in their quest for trout.

A few years later, Utah Division of Wildlife Resources’ Chris Crockett says, no one’s laughing.

The goldfish have taken over Maple Lake.

Swimming in the murky, low water near Payson, the estimated thousand goldfish stick out like, well, an orange fish in brown water. Most grow to about 6 to 8 inches — and they’re reproducing quickly, fighting with trout for food and mucking up the water quality as they forage.

As much as Crockett, an aquatics manger for the division, says he doesn’t like to kill fish, he said he has no choice. It’s the goldfish or the trout, and to rid the lake of the goldfish means taking the trout with them. That’s just what DWR officials are planning for the week of Oct. 15. They’ll hit the lake with a dose of the insecticide rotenone, hopefully wiping out the goldfish and every other fish. Then, Crockett said, they’ll reboot and restock it with trout in the spring.

Crockett said he isn’t sure how long the goldfish have been in Maple Lake, but anglers started reporting the nuisance fish in late 2015. He said officials knew there was a real problem that next year, when anglers were pulling more goldfish from the lake than sport fish. He suspects the original goldfish were unwanted pets, dumped into the lake by their then-owners, who thought they were doing the fish a favor.

Discarding goldfish into bodies of water isn’t uncommon. Crockett said officials all over the state deal with it to some extent or another, and it’s primarily a problem in lakes and ponds near urban populations. There are also goldfish in Spanish Oaks Reservoir, near Spanish Fork.

This is because, as Crockett said, “Very few people are willing to hike their goldfish really far away from a road or a campground.”

That act of “saving” the invasive goldfish, Crockett said, ends up wreaking havoc on lakes and ponds and often results in officials using tax dollars to exterminate the fish and later restock.

Given goldfish’s reproductive capabilities, Crockett said it’s likely the thousand-fish population in Maple Lake started when someone dumped just a “handful” of fish.

“Now,” he said, “you’ll see goldfish just covering half the lake — and those are just the ones that are visible.”

DWR officials also plan to use rotenone this month to rid the common carp from Pelican Lake, southeast of Roosevelt. An influx of carp into the lake in 2008 and 2009 has decimated the bluegill population, according to a news release. The lake will be restocked with bluegill and largemouth bass.

Officials commonly choose fall for rotenone treatment, Crockett said, because water volumes in lakes used for irrigation are lower, meaning crews can use less insecticide. Rotenone costs about $80 per gallon, and about a gallon is needed per acre-foot of water.