Goldfish were illegally released into an Idaho pond. Fish and Game will eradicate them

A pond in an Idaho state park near Almo will be closed for several months as officials deal with small fish that could become a big problem.

In a news release, the Idaho Department of Fish and Game said its Magic Valley Region will work with Castle Rocks State Park to treat the park’s fishing pond with a piscicide — a chemical meant to kill fish — to eradicate invasive goldfish that were discovered there.

“It’s unfortunate that we have to close public access to the Castle Rocks State Park fishing pond, but it’s necessary since goldfish were illegally introduced there,” said Tucker Brauer, regional fishery biologist with the Magic Valley Region. “This is our only recourse to re-set the pond to support sport-fish that anglers love to catch.”

The pond will close Jan. 20 and is expected to reopen in May. Officials said they’ll use a chemical called rotenone to kill all of the fish in the pond. When the treatment is complete, the pond will be restocked with hatchery fish for anglers to catch.

It’s the second time in recent years that Fish and Game has had to use rotenone to eliminate an illegally introduced goldfish population. In 2020, the agency did a similar project at Heagle Pond in Hailey.

Officials noted that illegally introducing fish into Idaho waterways can damage habitat and cost hundreds of thousands of dollars to mitigate. Offenders could be on the hook for those damages and can also be charged with a felony.