"They stocked whatever kinds of fish people wanted," said Dan Mahony, a biologist at Yellowstone National Park. The work began about 100 years ago.
Bucket biology, not the government, is suspected in the presence of lake trout at Yellowstone Lake.
Mahony said the fish, a threat to native cutthroat, are believed to have been in the lake for 25 to 40 years. The chain effect of nuisance fish reaches to Yellowstone's grizzly bears, which eat cutthroat during the spawning season.
Fish and wildlife officials say enforcement against bucket biologists is practically impossible unless people are caught in the act.
Lake trout at Yellowstone Lake are being netted to reduce the population, and in a reversal of the catch-and-release rule at many park fishing sites, anyone catching a lake trout must keep it.
At media magnate Ted Turner's Flying D Ranch in Montana, there are plans to poison all brook, rainbow and Yellowstone cutthroat trout from a lake and a lengthy stretch of creek. The nonnative fish planted years ago would be replaced with westslope cutthroat trout, which are in critical decline.
The $500,000 project, two-thirds of it funded by Turner, has been delayed while the state Department of Environmental Quality conducts an environmental analysis.
"We would be the first to admit that killing a bunch of fish is drastic," said Mike Phillips of the Turner Endangered Species Fund. "If westslope cutthroat trout were not so imperiled, such drastic measures would not be needed. But the species is in the tank and going down the tube."
Opponents object to removal of a productive fishery and cite water-quality concerns, saying they have no assurances about the ultimate safety of rotenone and antimycin, poisons commonly used in fish eradication. The Turner project, southwest of Bozeman, is exceptionally large, involving about 70 miles of Cherry Creek.
Biologists say painful lessons have been learned over the years, and fish introduction isn't done much anymore.
"Some people in fisheries management had the mistaken notion that there was an empty niche in this aquatic system, so maybe they should put a striped bass in to fill the niche," said Baltz, of the Fisheries Society. "But there aren't any empty niches, per se."