Populations of native cutthroat trout appear to be rebounding, thanks to an effort to kill off an invasive species in Yellowstone Lake. More than 40 species, including bears, river otters and eagles, rely on cutthroat trout for food. But Trout Unlimited special project manager Dave Sweet said cutthroat have been under attack.
“Yellowstone Lake is unique in that it only had primarily one species in it, which were Yellowstone cutthroat trout,” he said. “Some lake trout were introduced and simply started preying upon those cutthroat and diminished the populations from that 4 million number down to 5 or 10 percent.”
The National Park Service and conservation groups have been using large underwater nets to catch lake trout and kill them. They’re also finding out where they spawn.
“We implant the lake trout with transmitters that give off a hydro-acoustic signal and then monitor their movement patterns and in particular where they spawn in the fall,” Sweet said.
All these efforts are expensive—netting alone has cost the Park Service $2.5 million dollars already—but Sweet thinks it’s worth it.
“Just this last spring, there was a grizzly sow and cub who was videoed on, I believe it was west Thumb Creek, back in those tributaries, feeding on cutthroat again," he said. "That hadn’t been seen for many years. The grizzlies hadn’t bothered to go to those spawning tributaries because there weren’t any cutthroat there.”
There are now roughly equal numbers of the two species but the hope is to return the lake to its original ecosystem, with cutthroat trout its primary fish species.