Bucket biologists have taken it upon themselves to plant walleye in Swan Lake. Fortunately, two fish were caught, and if the culprits are caught, they could end up paying a hefty fine.

Region 1 Fisheries Manager Mark Deleray said FWP biologists caught the walleye during gill-net sampling last week. Both measured about 17 inches long, and Deleray didn't know how long they'd been there or how many more might be in the lake.

Walleye are not native to Swan Lake and could wreak havoc on the trout population since they are voracious predators of perch, minnows and small trout. In Canyon Ferry where they are allowed, walleyes eat more than 750,000 pounds of perch each year—that's about 4 pounds of perch per walleye.

Because introduced species can upset the natural balance, Montana has outlawed the unauthorized introduction of fish species. Penalties can range from fines of $2,000 to $10,000, loss of fishing, hunting, and trapping privileges, and liability for the costs to eliminate or mitigate the effects of the introduction

Last year, the Fish and Wildlife Commission strengthened FWP’s policy for dealing with illegal introductions. Within the next 30 days, biologists will try to confirm the presence and distribution of additional walleye and then decide how to either suppress or remove them.

Since one angler's favorite fish can eliminate another's, Montana Trout Unlimited got involved in 2013 after FWP discovered that someone had planted smallmouth bass in Seeley Lake, about 50 miles south of Swan Lake. At that time, the fine was only $1,000.

MTU stepped in and offered $10,000 for convictions because problem is getting worse. Of more than 500 known illegal introductions in Montana, one quarter occurred in the past 12 years. More than 50 species of nonnative fish have been introduced into 300 state lakes and streams.

Talk to people around Seeley Lake, and they have their suspicions about who did it. But It's often difficult for FWP to cite someone for doing illegal introductions without some telling evidence. So many illegal introductions go unpunished even though they sometimes lead to situations where FWP has to spend a lot of time and money correcting the problem.

That led the FWP commission to take a harder line on introductions.

Fortunately, not all introductions are successful. But Montanans don't want the walleye in Swan Lake to become like the scourge of lake trout in Yellowstone Lake.

Deleray asks anyone with information on who introduced walleye into Swan Lake to call 1-800-TIP-MONT. Callers do not need to identify themselves and may be eligible for a $15,000 cash reward. Anglers are encouraged to keep any walleye caught and report additional sightings of walleye to FWP at 406-752-5501.