Illegal Fish Plants Are A Nightmare For Anglers And Biologists

Jim Vashro, FWP Region 1 Fisheries Manager

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Ten years ago, two young anglers watched a man dump a bucket of fish into Lake Mary Ronan and drive away. Hurrying to the spot, they saw yellow perch swimming around. They had just witnessed an illegal fish introduction.

The two young anglers contacted the local game warden and within a few hours biologists chemically treated the cove with rotenone, killing nearly 50 perch, bass, and rainbow trout. Unfortunately, at least a pair of perch escaped.

This and other illegal introductions of fish introduce harmful competition and interbreeding with native species, disrupt spawning and may carry and spread diseases or parasites and reduce fishing opportunities. It is illegal to import and release any wildlife in Montana without FWP authorization.

At least 20 percent of the illegal fish introductions documented by FWP have occurred in the past 10 years. In total there are 426 unauthorized fish introductions in 251 waters across the state, involving 49 species of fish. Northern pike and yellow perch account for more than 40 percent of the introductions, but there have been recent surges in the appearance of several minnow species and walleyes. On the extreme end of the spectrum, tropical fish such as pacu and Oscars are also showing up.

Fast-forward to 2002 at Lake Mary Ronan. In the 10-year interim, perch numbers have exploded and now dominate the lake. Biologists have captured as many as 215 perch in a 150-foot long net and estimate that perch make up 70-90 percent of all catches. The Kokanee Salmon catch per net has declined each of the last four years and is now only 30 percent of what it was in 1998. Rainbow trout counts have also declined.

Lake Mary Ronan, one of the most popular lakes in northwest Montana, once produced 18,000-25,000 days of fishing for trout and salmon each year and 1-4 million Kokanee salmon eggs for the state hatchery system. Now the lake’s popular fishery is in question.

Perch anglers are delighted to have a new place to fish. And, the perch are now averaging a respectable eight inches due to a strong year class. But perch have a history of stunting after the first good crop.

Of the 56 perch populations in Region One, only about five produce reasonable fishing. The odds are not good in the long run for perch anglers. Kokanee anglers are understandably disgusted. Even though the Kokanee are getting larger, a sign that overall numbers are declining, anglers have a hard time getting through the perch to catch a salmon.

Resort owners are understandably nervous about the economic impact. And, there are other hidden costs. Hatcheries are now raising half the stocked salmon to an inch longer to withstand perch predation and competition. Hatcheries are out of space and the larger fish cost thousands of dollars more to raise and transport. Biologists estimate it would cost $1.3 million to rotenone the entire lake, with no guarantee of success.

All this damage is the result of one guy with a bucket of fish.

FWP recently adopted a policy that calls for aggressive prosecution and restitution for illegal fish plants. FWP will remove the unwanted fish, if at all possible. Failing that, FWP may attempt to suppress the illegal fish by waiving fishing limits, banning fish derbies, halting the stocking of any related or affected fish species, and by encouraging commercial fishing. Anglers can do their part by disposing of bait-fish properly and by calling 1-800-TIPMONT to report any suspicious activities.