Illegal Fish Introductions

Illegal introduction of non-native species is also of great concern. Fish like carp, yellow perch, suckers, shiners, sunfish and even certain game fish can severely affect sport fisheries. When people move live fish from one body of water to another, the future of their own fishing is at stake. Anglers illegally introduce species by using live bait, dumping bait buckets and even intentionally stocking rivers and lakes.

Bucket biology – the practice of transporting live fish from one water body to another to artificially stock the second water body – IS A CRIME. You can be arrested and fined heavily in Montana and you can cause significant damage to a fishery. Introduced fish may:

  • Cause the decline of many threatened and endangered species;
  • Reproduce rapidly and outcompete native species;
  • Interbreed with native or established species, thereby reducing the long-term survival of native species;
  • Carry and spread new diseases and parasites;
  • Directly alter the existing habitat;
  • Require difficult and costly management decisions that may or may not be successful in restoring native fishes.

Since the discovery of Walleye in Swan Lake, Montana Fish, Wildlife & Parks, Montana Trout Unlimited and the Fishing Outfitters Association of Montana joined together to offer rewards for information leading to the prosecution of persons illegally introducing fish into any Montana waters.

Swan Lake. Photo courtesy Lori Curtis


Walleye in Swan Lake
In 2015, illegally introduced non-native walleye were discovered in Swan Lake during a Montana Fish, Wildlife & Parks contracted netting operation. The professionals are hired to remove lake trout from Swan Lake three times a year in an effort to protect populations of native bull trout and kokanee salmon. The fall netting targets lake trout spawning areas during a time when bull trout have migrated from the lake to their spawning streams. Non-native lake trout eat bull trout and other species and have few predators to keep them in check.

Lake trout were introduced to Flathead Lake as a sport fish in the early 1900s. They took off in the 1960s after mysis shrimp were introduced to Swan Lake and Whitefish Lake and later drifted downstream to Flathead Lake. They became food for lake trout which quickly grew to the dominant species in the 1980s. Flathead Lake’s kokanee population was nearly wiped out within three years. Lake trout appeared in Swan Lake in 1998. That same year, bull trout were listed as “threatened” under the U.S. Endangered Species Act.

According to Montana Fish, Wildlife and Parks Region 1 fisheries manager, Mark Deleray, “bucket biologists” have cost the state hundreds of thousands of dollars in attempts to remove the predators and preserve existing fish populations. It is illegal to move any live fish from the water in which the fish are caught. Montana Trout Unlimited Past-Executive Director Bruce Farling said “There have been over 600 documented, illegal introductions of unwanted species in the waters of this state in recent years, and in all cases, either the fisheries were damaged or no better fishery was created. This introduction puts a multimillion-dollar fishery at risk.”

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