Yellowstone National Park unleashed bionic lake trout into Yellowstone Lake three weeks ago in an effort to pinpoint where the invasive trout spawn, so the park can then kill them en masse.
"The crux of this research and the whole suppression effort is to restore the Yellowstone cutthroat trout," says U.S. Geological Survey biologist Bob Gresswell. "I think there are myriad reasons to do that. Certainly the most basic is the role the Yellowstone cutthroat trout plays in the Yellowstone Lake ecosystem."
Yellowstone cutthroat trout are a primary food for an array of critters. Park fisheries biologists say lake trout, believed to have been introduced in the '80s, have out-competed Yellowstone cutthroats to the point where there are fewer cutthroats in Yellowstone Lake then ever before. That means there are fewer cutthroats in the ecosystem's tributaries, where grizzly bears, otters, osprey, eagles and other animals eat them. Scientists say grizzlies aren't feeding from streams as much as they used to.
For years the park has relied on gill-netting to cull lake trout. Last year it harvested 140,000, says Gresswell. So far this year it's around 165,000, and that number could top 200,000.
The new effort, supported by a number of conservation groups, including Montana Trout Unlimited, targets lake trout larvae and embryos. Gresswell and his research team cut open 140 lake trout, inserted transmitters, and released them back into the lake. At the same time it sunk 28 receivers into the lake, attached to buoys. Whenever a bionic lake trout comes within 500 meters of two receivers, triangulation determines the fish's exact location. The data will, theoretically, reveal where the lake trout spawn. The first batch of data was expected this week. Researchers are using Bluetooth technology to wirelessly extract the data from the receivers.
The point is to restore cutthroat trout numbers, says park fisheries biologies Todd Koel, "but the bigger issue is to get the ecosystem back on its feet, and get the bears using cutthroats as a food source again."