YELLOWSTONE NATIONAL PARK, Wyo. (AP) — Park rangers netted a record number of lake trout out of Yellowstone Lake this year.

The large trout are invasive and devour native cutthroat trout, which are an important food source for grizzly bears and osprey. The National Park Service has been trying to eliminate lake trout from the lake, netting more than 268,250 lake trout since 1994.

This year, crews netted 73,279 lake trout — 13,000 more than last year and twice the number netted two years ago, according to Patricia Bigelow, a Yellowstone fisheries biologist.

But even with record numbers of lake trout being caught, the netting only seems to be curbing the species' explosive population. Biologists base that conclusion on the rate at which lake trout are being caught.

"That bothers me the most," Bigelow said.

There have been signs of hope for cutthroat trout, though. Bigelow said checks at 11 sites around Yellowstone Lake this year revealed more Yellowstone cutthroat than since 1998.

Also, fewer large lake trout were caught this year, indicating that fewer big fish with big appetites might be in pursuit of cutthroats.

The biggest lake trout caught this year was 22.4 pounds.

Lake trout are natives of the Great Lakes and were first confirmed in Yellowstone Lake in 1994. The Park Service spends $400,000 a year on the gill-netting program.

Each May to October, crews on two boats ply Yellowstone Lake with nets with openings small enough to catch lake trout by the gills but large enough to let most cutthroat through.

Crews were out earlier than usual this year after learning that lake trout are especially active just as the ice melts on the lake. Bigelow said they netted more than 10,000 lake trout in the first five days this season.