Sidebar by Hal Walter
Wildlife – October 1999 – Colorado Central Magazine
Four strains of cutthroat trout are native to Central Colorado waters, yet the Colorado Division of Wildlife places an emphasis on stocking rainbow trout, native to the West Coast.
Why Californicate the fishery? While many believe the rainbow is superior in “sporting qualities,” the truth is that simple economics makes it the trout of choice for mass production, the figurative feedlot cattle of the industrial-recreation racket.
According to Del Canty, fisheries biologist for the Delta-Montrose Vo-Tech School, rainbow trout are the best of the trout family at adapting to hatchery conditions.
“They took to the food the best and grew the fastest in the crowded conditions,” Canty says of the grain-fed, raceway-raised rainbows.
Ironically, it’s this hatchery life that makes the rainbow the most likely trout to catch whirling disease. While any member of the salmonid family can be infected, the fish-farm rainbow gets whirling disease more often because the crowded, slightly warmer hatchery waters are often the perfect climate for propagation of the spores.
“It’s a certain temperature of water that causes the problem,” says Canty. “And that’s the exact temperature the hatcheries like to raise these fish at. A little colder and they’re not affected quite as much, but they grow faster in (slightly) warmer water.”
Whirling disease originated in Europe and is spread by birds among waterways — including fish hatcheries. Canty says that members of all strains of trout can develop a resistance to the disease if allowed to. He says the problem in Colorado is that fish hatcheries are attempting to eradicate the disease rather than foster populations of fish that are resistant to it.
“The best bet is, if you have it, just continue to raise fish and let those that will develop immunity to it live, and let the others die,” Canty says. “The tactic here was to eradicate it and it’s impossible to do simply because birds carry it. Anytime a disease is carried by birds, and you can’t control birds, you better say let’s go with the immunity, let’s raise fish with the immunity.”
What about bringing back the natives? The Leadville National Fish Hatchery has been raising a strain of Snake River cutthroat trout that seem to be less susceptible to whirling disease, but this only points out yet another downfall of industrial fish-rearing — cross-breeding of different strains of trout.
Of the 14 original subspecies of cutthroat trout identified by Patrick C. Trotter in his book, Cutthroat — Native Trout of the West, four were native to Central Colorado. The area is interesting to cutthroat trout researchers because the headwaters of four different major continental watersheds flow from this relatively small area. In each watershed, separate strains of native cutthroat trout were isolated.
In the Arkansas drainage, now populated largely by brown and rainbow trout, the greenback cutthroat was prevalent. A threatened species, the greenback is now found in closely watched, isolated populations in Colorado. Similarly, there are pure Colorado River and Rio Grande strains of cutthroat endemic to those watersheds, but now found only in isolated populations. In addition, the yellowfin cutthroat subspecies, thought to have originated in Twin Lakes near Leadville, is now extinct.
Even the “native” cutthroats found in the higher lakes and streams aren’t exactly native, probably Yellowstone-strain cutthroats or a Heinz 57 blend of other subspecies, brought in through stocking programs over the years. Anglers also sometimes catch “cutbows,” hatchery-created hybrids of the cutthroat and rainbow trout.
The irony here is that, according to Canty, both rainbow and cutthroat trout evolved from the West Coast salmon.
In light of that, it’s only taken man about one century to undo what it took nature hundreds of thousands of years to accomplish. –Hal Walter