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Montana fights illegal dumping of non-native fish into the state's lakes

33m

Summary

  • People are illegally dumping non-native fish into Montana's lakes, a practice called bucket biology, harming native fish and the animals that depend on them.
  • In 1992, yellow perch dumped into Lake Mary Ronan wiped out the lake's native Westslope cutthroat trout population.
  • Intentionally introducing non-native fish is a felony in Montana, but no one has been charged or convicted there.
  • Montana Fish, Wildlife, and Parks fights dumping with bounties, otolith forensics pioneered by biologist Sam Bourret, and modeling of vulnerable lakes.
  • Flathead Lake, one of the world's clearest lakes, is managed by the state and the Confederated Salish and Kootenai Tribes; non-native fish already outnumber native ones there.

Reactions

  • Craig Barfoot, fisheries program manager for the Confederated Salish and Kootenai Tribes, said one person's decision can affect an ecosystem, like an act of arson.
  • Sam Bourret said fish dumpers are likely avid anglers officials probably know, and that some appear spiteful in wanting to move fish around.
  • Some anglers say introduced fish like northern pike and walleye are more fun to catch than Montana's native fish.
  • The writer concluded the future of Flathead Lake and similar lakes depends on what people decide to do with their buckets.

Timeline newest first

  1. In October 2026, a writer visiting Flathead Lake Biological Station heard biologists describe an avoidable catastrophe in the making from illegal fish dumping.
  2. Earlier in 2026, biologists on Sam Bourret's team at Montana Fish, Wildlife, and Parks removed 4,000 goldfish from a hotel pond on the Thompson River.
  3. A 2025 survey found Flathead Lake is clear down to about 36 feet.
  4. In 1992, a man dumped a cooler of yellow perch into Lake Mary Ronan; two teenagers reported him and each received a $500 reward.
  5. Biologists tried to kill the Lake Mary Ronan perch with nets and poison, but at least two survived, multiplied, and wiped out the lake's Westslope cutthroat trout.
  6. The Lake Mary Ronan dumper was fined for illegally introducing non-native fish; Montana later made the offense a felony punishable by up to two years in prison or a $25,000 fine.
  7. In the 1970s, Montana decided to stop stocking non-native fish in most of its streams and rivers.
  8. Starting in the late 1800s, wildlife managers stocked lakes with hatchery fish; about 30 non-native kinds were introduced to Flathead Lake, a dozen of which established populations.

Sources newest first

  • Why do people keep dumping buckets of fish into Montana’s lakes?vox.com· 33m

    Vox's November 15, 2026 article by Neel Dhanesha examines "bucket biology" — people illegally dumping non-native fish into Montana's lakes — and the damage it does, as when yellow perch dumped into Lake Mary Ronan in 1992 wiped out its native Westslope cutthroat trout. Officials are fighting back with bounties, fish forensics pioneered by Sam Bourret, and outreach, though Dhanesha concludes the future of Flathead Lake and lakes like it depends on what people do with their buckets.