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 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





Meet the Author
Cathy Newman began her career writing for the Miami News, before joining the staff of National Geographic Magazine where she was Editor at Large. In addition to dozens of articles for the magazine, she is the author of three books for National Geographic. Perfume: The Art and Science of Scent, Women Photographers at National Geographic, and Fashion. She is a regular contributor to Smithsonian Journeys.