A survey of the George River caribou herd in Labrador and Quebec shows the number of animals dropped by half from 2015 to 2013.

There are 10,200 caribou left in Labrador and Quebec as of fall 2015, said the Newfoundland and Labrador Department of Environment and Conservation in a news release Friday.

That compares to 20,000 two years before.

"A grave concern," said Minister of Environment and Conservation Perry Trimper, who added survival rates are up in young caribou, but overall numbers continue to decline.

The large male population has dropped to five per cent, down from nine per cent in 2014, and overall adult mortality remains high at 30 per cent, according to the latest survey.

"Across Canada and around the world, caribou herds are all on the decline right now," said Trimper.

perry trimper

The Minister of Environment and Conservation, Perry Trimper, says the decline is a grave concern. (Sherry Vivian/CBC)

"We don't suspect there's anything unusual other than a natural, and I guess I would use the word phenomenon here, because we don't understand why and how this occurs."

A five-year ban on hunting was imposed in 2013, but there have been charges of illegal hunting.

A case against 10 hunters from Sheshatshiu is due to be heard in provincial court in Happy Valley-Goose Bay on Monday.

"Any hunting right now is a concern," said Trimper. "We're just asking for everyone's co-operation to leave the herd alone right now."

He said the governments of Newfoundland and Labrador and Quebec will continue to work with with aboriginal governments and organizations on future conservation strategies.

The plan includes sending officials into northern communities to explain why the ban is in place.

"No one wants to see this happen on their watch," said Trimper.