Continued state stocking of nonnative fish threatens Maine’s iconic species

By Bob Mallard

Nothing threatens Maine’s wild native fish, and fishing in general, more than nonnative fish introductions. Nonnative fish alter aquatic ecosystems considerably, and often permanently. And once introduced, they can spread throughout a watershed, infecting more waters.

So-called bucket biology, or the deliberate stocking of fish by anglers, gets most of the attention. It is illegal, and the folks doing it know they are breaking the law — they just don’t care. Informational signage and the threat of fines can help make some reconsider, but far more needs to be done.

The deliberate illegal use of live fish as bait is another problem, but it is not easy to address as those doing it are knowingly violating the law. The accidental illegal use of live fish as bait has the same effect as the deliberate illegal use. 

There is another form of nonnative fish introductions that is as ecologically harmful as bucket biology and the use of live fish as bait. I am talking about the state-sponsored stocking of nonnative fish, something most accept without question.

It has accounted for hundreds of nonnative fish introductions in Maine, most of which are at the expense of wild native fish.

In some cases, stocking of nonnative fish by the Maine Department of Inland Fisheries and Wildlife has resulted in the creation of self-sustaining populations. In other cases, while the fish do not naturalize due to a lack of spawning habitat or other factors, ongoing stocking has basically the same effect as a self-sustaining population.

The impact of state stocking of nonnative fish goes beyond the ecological damage. It makes it harder to promote and defend the critically important message that moving fish around is a bad thing.

Nonnative fish stocking is rooted in the flawed belief that trout (including Arctic charr and salmon) should be unlimited, and that fish from other areas, including outside the country, are somehow better than what exists here naturally. It is compounded by the belief of state fisheries managers that they can do a better job than Mother Nature of managing our resources. 

Many historic nonnative fish introductions in Maine were state-sponsored. The federal government also played a role and, arguably, started the ball rolling. While federal fisheries managers now support wild and native species, DIF&W unfortunately is still stocking nonnative fish over wild native fish, resulting in competition for food and space, predation and, in some cases, spawning disruption. 

An analysis of the DIF&W species database, which has one record for each water/species combination (lakes and ponds only), found 366 entries classified as “Legal Transfer,” which is different from “Actively Stocked” and “Historically Stocked.” 

One of the more questionable examples of the state stocking of nonnative fish is Moosehead Lake, where landlocked salmon are being stocked over wild native brook trout. Moosehead is the second-largest native brook trout lake located entirely within the United States after Lake Michigan.

Nonnative landlocked salmon are being stocked in historic Rangeley and Richardson lakes, both native brook trout waters. Stocked salmon from Lower Richardson Lake are leaking into the fabled Rapid River, the most significant wild native brook trout river fishery in the nation, where the population is already stressed by an illegal nonnative smallmouth bass introduction.

Nonnative landlocked salmon were stocked in Mooselookmeguntic Lake up until the early 1980s. Since then, the salmon have naturalized, overpopulated and stunted, causing local sporting organizations to call for formal culling events, and DIF&W to impose a “no size or bag limit on landlocked salmon less than 16 inches” regulation. 

Possibly the most egregious example is the ongoing stocking of nonnative lake trout in Green Lake in Hancock County, which is one of only 12 wild native Arctic charr waters left in the contiguous U.S. 

Introduced lake trout are blamed for the demise of Arctic charr, formerly known as Sunapee trout, in New Hampshire and Vermont. Nonnative lake trout and smelt are also imperiling Arctic charr in Bald Mountain Pond in Somerset County. 

The state has accidentally stocked other waters with nonnative fish, including landlocked salmon in Deboullie Lake, putting three of the 12 remaining wild native Arctic charr populations at risk. Thankfully the salmon did not naturalize. While not deliberate, it shows the potential danger in regard to moving nonnative fish around. 

To put the scope of state-sponsored nonnative fish stocking and introductions in perspective, Maine historically was home to only four native landlocked salmon waters. Today there are roughly 10 unconfirmed populations, more than 100 waters where salmon are “present,” approximately 200 waters where they provide a “principal” fishery, and another roughly 85 where the fish failed to take hold and stocking was suspended.

Smelt, the primary forage for landlocked salmon, can now be found in more than 500 Maine waters, none of which are stocked. An anadromous species, the landlocked lifeform is more likely to have been introduced than not. 

Brown trout, a species not native to the U.S., are said to occur in more than 150 waters in Maine. Nonnative rainbow trout, native to west of the Continental Divide, can be found in roughly 30 waters.

Regardless of who’s introducing what and where, and whether it’s illegal, legal, accidental or incidental, when it comes to nonnative fish stocking and introductions the result is almost always the same — we end up compromising the native fish, exchanging one species for another or, worse, destroying the fishery altogether. 

When it comes to moving fish around, we need to stop trying to play God. And this means state agencies as well as anglers. The state cannot effectively ask the public not to do what it is doing. It’s time to walk the walk, not just talk the talk, as the current strategy is clearly not working.