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Invasion of the (Trout) Aliens

It is in the nature of human hubris to assume Man Knows Better than Nature.

Which is why, perhaps, when it comes to trout, things are a downright mess.  Thanks to the British, as the Empire expanded beyond the sunset, so did trout. In 1864, they were introduced to Tasmania, India in 1889 and South Africa in 1890.  Trout traveled to places no trout swam before.

Brook trout caught and released
Brook trout are among the smallest of their group, but many people consider them among the most beautiful. Photo: Marc Peter, MyShot

That wasn’t all. In the 1880s, European brown trout went to America, while American rainbow trout came to Britain. The biological bouillabaisse has been stewing, says Stephen Moore, Supervisory Fisheries Biologist at Great Smoky Mountains National Park, ever since Roman times. (The Romans transferred salt-water mullet and lamprey—species that could tolerate freshwater—into natural lakes.)

“There’s a long history of tinkering with fish populations,” Moore says. “We’ve put fish into habitats where there were no fish, and we’ve put non-native species on top of natives. The thinking was: ‘God made a mistake and didn’t put our favorite fish there.”

Spoiler alert. The species shuffle causes biological havoc. Non-natives out-compete natives in every situation. “It took man a long time to realize that once the non-natives are free and establish reproducing populations that it is impossible to turn the clock back,” says Moore. “Our only hope is where feasible to restore segments of historic range for native species like brook trout.”

The brook trout, specifically the Southern Appalachian brook trout, is Moore’s favorite fish. They are vibrantly beautiful with orange bellies and fins, flanks dotted with red surrounded by a halo of blue.  They also represent Moore’s 30 year-long commitment to restoring them to their native habitat.

Upsetting Fish in the Smoky Mountains

When large-scale logging in the Smoky Mountains at the turn of the century stripped shade-providing streamside vegetation, summer water temperatures rose to intolerable levels for the fish; sediment from the eroded banks clogged spawning gravel impairing their ability to reproduce. Brook trout all but vanished from waters at elevations below 3,000 feet.

To mitigate the damage, well-meaning logging companies restocked streams with rainbow trout, further compounding the problem when the aliens out-competed and interbred with the remaining brookies.

As if things weren’t bad enough, acid rain from the region’s coal-fired power plants and nitrates from agriculture contaminated the water, adding to the trout’s litany of woes. Native brook trout lost about 75 percent of their range.  Nothing short of an aggressive restoration campaign could provide a fix.

Eagle taking brook trout
Brook trout can be an important part of an ecosystem, as on Lake Nipigon in Ontario. Photo: Bill Marzana, MyShot

Restoring Brook Trout

The fix began in 1976, right at about the time Moore began work for the National Park Service as a young graduate student. He eventually became the head of a program that combined electro-shocking shallow streams and the use of antimycin in deeper waters to weed out the invaders, and then restocked streams with native brook trout. Careful monitoring of water quality and tightened EPA regulations regarding air pollution helped, too. So far, says Moore, more than 27 miles of historic brook trout range has been restored, with another 15 to 20 miles to go.

It’s a win-win for fish and man. Trout, you see, are the mine canaries of fresh water.  When there is trouble in the environment, they are the first to go. When trout are where they ought to be, all is right with the world.

Brook trout in the Enfield Fish Hatchery in Maine
Brook trout in the Enfield Fish Hatchery in Maine. Photo: Pamela Wells, MyShot
Garter snake attacking brook trout
According to the photographer, this garter snake caught a brook trout, but was ultimately unable to swallow it. Photo: Tianne Strombeck, MyShot




  1. Stephen Amaral
    Crossville, TN
    September 24, 2013, 3:22 am

    The Southern Appalachian Brook Trout Hatchery: http://brooktrouthatchery.wordpress.com/
    The Tennessee Aquarium Conservation Institute: http://www.tnaci.org/
    They are involved with the Southern Appalachian Brook Trout Restoration Program. Additionally they are involved in other in other restorations: Placing “Lake Sturgeon” back into Tennessee waters and lakes.

  2. pesfls
    March 27, 2013, 11:08 am

    Hyperbole or not the basic premise of the piece is fair. In the west, though, it’s the opposite impact. Introduction of brook trout & german browns have decimated rainbows in many streams. Mature browns feed on rainbows and when brooks fertilize rainbow eggs the offspring are sterile thus further reducing rainbow population. It’s a mess.

  3. Mark T Keend Sr.
    March 17, 2013, 3:36 pm

    Wow look at the fish he looks like he is a little pissed off about the hole thing.

  4. Dan Auerbach
    March 2, 2013, 1:59 pm

    Incorrect hyperbole like:

    “Non-natives out-compete natives in every situation”
    “When there is trouble in the environment, [trout] are the first to go. When trout are where they ought to be, all is right with the world.”

    needlessly undermines the credibility of an otherwise worthwhile perspective on the long history of our direct manipulation of aquatic fauna.

  5. RR
    March 1, 2013, 8:34 am

    Please check out some of the work going to restore the habitats of Brook Trout in this country as well as other fish through the National Fish Habitat Partnership and Eastern Brook Trout Joint Venture. Fish habitat needs conserved now more than ever!


  6. FortSouthBend
    Out West
    February 27, 2013, 8:16 pm

    Quick, probably moot, note to those that might care… While Brook Trout numbers can be reduced by introduction of Rainbow Trout, they will not hybridize. They will hybridize with Bull Trout, Lake Trout, and Brown Trout however. Rainbow Trout can cause problems by hybridizing with other fish outside of their native range (Cutthroat, Apache, and Gila Trout) and are a threat which could lead to genetic extinction.