By Laura Zuckerman

SALMON, Idaho (Reuters) - U.S. wildlife managers at Yellowstone National Park are reporting an unusually high number of grizzly bear deaths, 55, linked to humans this year in a trend believed tied to a growing number of the bruins harming livestock or challenging hunters over freshly killed game.

The uptick in bear deaths comes as the Obama administration says the population of roughly 690 bears in and around Yellowstone has come back from the brink of extinction and should be stripped of U.S. Endangered Species Act protections.

  The plan, proposed by the U.S. Fish and Wildlife Service earlier this year, opens the way for hunting in Wyoming, Montana and Idaho, the Northern Rocky Mountain states that border the park.

The measure is strongly opposed by conservationists and Native American tribes but supported by sportsmen and ranchers who claim the number of conflicts will diminish by targeting bears that bounce hunters off freshly shot game or which harm livestock.

The carcasses of at least 55 Yellowstone area bears have been found so far this year, with most dying from human-related activities, according to figures compiled by the U.S. Geological Survey. Nearly half the grizzlies were killed by government bear managers for preying on cattle, sheep and the like.

Wildlife advocates fear that the final tally for 2016 will exceed the 61 bears known or believed to have died in the Yellowstone area last year, a high in the decades since such moralities have been tracked.

That compares to 28 grizzlies known or likely dead in 2014 and 29 in 2013, according to government records.

  Gregg Losinksi, member of a federal and state team that oversees Yellowstone grizzlies, said some bears running into conflicts are seeking to expand their range into areas already occupied by humans or other grizzlies.

  "As far as we're concerned, the population is maxed out based on the available habitat and we're seeing more and more deaths because of this density," he said.

Conservationists say they are alarmed by the number of Yellowstone area bears that have died in 2016, the third year the overall population has fallen.

"The mortalities keep escalating and the population keeps dropping. We don't think now is the time to remove Endangered Species Act protections; we need more time to study these trends," said the Sierra Club's Bonnie Rice.

(Reporting by Laura Zuckerman; Editing by Dan Whitcomb and Sandra Maler)