A lot of well-deserved attention has been given to Aquatic Invasive Species (AIS) such as zebra mussels and Eurasian watermilfoil. A new species in the wrong place can dramatically alter an aquatic community. But when I talk to anglers about illegal fish introductions I either get a blank look or a shrug of the shoulders. And that’s too bad, because illegal fish are hurting aquatic communities across the state and are costing you opportunity and money.
Although people don’t seem to recognize it, fish are subject to the same laws of nature as deer and humans. The primary law is carrying capacity. A body of water can only raise so many pounds of fish, either lots of little ones or a few big ones. Carrying capacity may fluctuate a little by year due to weather and other limiting factors but it doesn’t change much. Add a new fish species and some existing species has to reduce by a similar amount. No free lunch, no exceptions.
Put another way, it takes about 100 pounds of perch to grow a 10 pound walleye (or 2 five pound walleyes). Many of the illegal fish are top level predators so you give up a lot of opportunity and harvest (perch) to catch a few predators (walleyes). In a typical illegal introduction, the first few fish have few limiting factors and show almost unlimited growth. This leads to early angler predictions of a water full of new state records. As year classes fill in and numbers increase density dependent growth kicks in and fish growth and average size drop dramatically. Often you end up with a water full of stunted fish like perch or brookies.
Many illegal introductions are due to ignorance of the biological rules noted above. Many are careless or thoughtless moves like dumping a bait bucket. But many are planned and result from a sense of entitlement, that a fisherman can have the species he wants anywhere he wants. Private ponds are an increasing source of problems as pond owners try to circumvent private pond rules that protect existing state fisheries.
In Canyon Ferry Reservoir illegal walleyes knocked out the perch fishery and drastically reduced rainbows. Those two fish consistently put Canyon Ferry in the top 3 lakes in the state, what were bucket biologists trying to improve? After an initial boom of big walleyes the fishery is now going through boom and bust cycles. With walleyes, shore and winter fishing have both declined. Rainbows have been stabilized but only by increasing the size of plants from 4 inches to 8 inches. That change costs $200,000 more a year than previous and also takes up most of the supply of catchable rainbows needed elsewhere in the state. Twenty years later and spending the equivalent of more than 11,000 fishing licenses a year, fishing pressure is just back to what it was before walleye.
Still think illegal plants don’t affect you? Avista Corporation owns and operates Noxon Rapids Reservoir on the Clark Fork River just upstream of Idaho. For more than 10 years Avista has been running a native trout (bull and westslope cutthroat) restoration program with FWP and US Fish and Wildlife Service, spending more than $60 million absorbed by ratepayers. Walleye were illegally planted and are now increasing rapidly. Perch, both a popular fishery and a good prey source, are declining rapidly. That puts largemouth and smallmouth bass, which support 7-8 derbies a year to help the economy, at risk. Even more at risk are the cutthroat and bull trout which enter the reservoir through bays where walleyes lie in wait. The Noxon bull trout are important to Montana’s push to delist the species from the Endangered Species Act. The bull trout’s Threatened listing affects many federal and state actions such as timber and natural resource development, road building, dam operations and so forth.
The real key is prevention. Illegal plants are costly to eliminate at best and often can’t be reversed. If you consider the impacts I’ve described above and multiply that by the 250 waters with illegal fish you can see the costs that Montana sustains, both in increased management and lost opportunity. Yet illegal plants continue, I’ve heard of a half dozen more just this summer.
Educate yourself, don’t move live fish which is generally illegal anyway. Talk to your fishing partners and report anyone you know is moving fish through 1-800-TIPMONT (847-6668). Penalties need to be stiffened more to reflect the economic impact of illegal fish plants. AIS programs need to increase the focus on illegal fish which are just as devastating as the other species currently watched for.
It’s time to kick the bucket.
This article by Jim Vashro, MWF Board Member and former regional fisheries manager for Montana Fish, Wildlife and Parks in northwest Montana for more than 30 years, is a summary of his full article which appeared on page 3 of MWF Fall 2015 Newsletter.