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Illegal Introductions

A Fishery Manager's Nightmare

What's the Problem?

Montana's lakes, rivers and streams constitute a multi-million dollar source, which we all enjoy. Our sport fisheries are among the finest in the world. However, when people illegally introduce fish to these waters, they jeopardize those fisheries.

Illegal introductions cause serious problems. Fish like carp, yellow perch, suckers, shiners, sunfish, and even certain game fish can severely affect a sport fishery. So, when someone moves live fish from one body of water to another, the future of their fishing is at stake.

Some of the earliest fisheries management in the United States centered on the introduction of game fish. In fact, 1989 marked the centennial of the arrival of rainbow and brown trout to Montana's waters. Those introduced trout are the foundation for Montana's internationally famous fishing. Our waters have also been planted with northern pike, walleye, bass, crappie, sunfish, golden trout, salmon, yellow perch and carp, among others.

Some introductions are planned management plants that benefit certain waters. But in some cases anglers have illegally introduced species by using live bait, dumping bait buckets and even intentionally stocking rivers and lakes.

Why Not Introduce Species?

Moving live fish or aquatic invertebrates (insects) from one body of water to another is a CRIME. You can be arrested and fined for any such activity in the state of Montana.

There are important reasons for this law:

  • Introduced fish may compete with native or already established species.
  • Introduced fish may behave differently in a new habitat -- they may not improve and are likely to harm the fishery.
  • Introduced fish may hybridize (interbreed) with established species.
  • Introduced fish may carry and spread new diseases and parasites.
  • Introduced fish may actually alter the existing habitat.
  • Illegal introductions can raise management costs by requiring planting more or larger fish or even chemical rehabilitation to maintain or restore the fishery. The result is less fishing opportunity and higher costs for anglers.

In Montana, fisheries managers emphasize preserving and enhancing wild fish populations. They also give special consideration to populations of native fish, and Montana is the home of many valuable native species: white sturgeon, mountain whitefish, grayling, bull trout, and cutthroat trout, among others. Montanans should take pride in their natural fisheries.

Because of our rich fishery resource, the Department of Fish, Wildlife and Parks maintains a cautious attitude toward any introduced species. Introduced fish can pose a threat to our valuable, natural fish and aquatic resources. When we introduce a new species to our waters, the native fish and habitat can suffer.

What Can Happen?

We need not look far to find some examples of the damage illegal introductions can cause. Carp were introduced in the 1880's as a game and food fish but have caused major problems in the Missouri and Yellowstone drainages. They feed by rooting on the bottom, causing turbidity and destroying vegetation. They also eat insects and fish eggs.

Some anglers illegally introduced northern pike into Lone Pine Reservoir in northwestern Montana in 1953. Since then the pike have spread or have been illegally transplanted into 54 additional bodies of water in the Flathead, Kootenai, Clark Fork, Bitterroot and Clearwater drainages.

In addition, there are many more examples of previously strong trout fisheries that have been severely damaged by the introduction of yellow perch, shiners and sunfish. These fish often over-populate and stunt. At the same time, the trout show slower growth and lower survival. Thus, the fishery provides less overall recreation.

Native cutthroat trout and grayling populations have declined in some regions due, in part, to the introduction of non-native trout species (brown, brook and rainbow) in the early 1900's. Even the introduction of invertebrates can pose problems. Introduced crayfish can eat aquatic insects and fish eggs, as well as destroy aquatic plants and increase turbidity. The introduction of leeches, fresh-water shrimp and other insects also could upset the aquatic food chain.

Planned management introductions have greatly improved our fisheries. Careful consideration is given to information on existing fish populations, habitat availability, and potential for harmful interactions with existing fish populations before the introductions are equally endangered by unwanted species.

What's the Point?

Whatever lakes or streams you visit, remember two important "don'ts" and one important "do".

  • Don't move live fish or aquatic invertebrates (insects) from one body of water to another for any reason.
  • Don't release any aquarium fish or bait fish into natural waters.
  • Do report any such moves you see or hear about as soon as possible.

Make your reports to:

Montana Department of Fish, Wildlife and Parks
1420 East 6 th Avenue
PO BOX 200701
Helena MT 59620-0701
406-444-2449

Or call toll free:

1-800-TIP-MONT
(1-800-847-6668)