The brawny bruins on the Alaska Peninsula are ready to brawl it out to see which will win this year’s fattest bear title in the wildly popular annual online voting contest known as Fat Bear Week.

The main event featuring adult bears starts next week, but first up Thursday is what the National Park Service calls a “chubby cubby appetizer,” Fat Bear Jr. Voters can cast ballots through Friday for their favorite adolescent ursine, with the winner advancing to the big show.

The contest, which began in 2014, is meant to showcase the resiliency of the brown bears, which pack on the pounds each fall to survive the harsh winter by gorging on salmon in the remote Brooks River in Katmai National Park and Preserve. The public can watch the bears on livestream cameras.

“It really is an opportunity for people to think about how bears survive, what they need to do to survive, what the ecosystem provides them and look at their individual success stories, as well,” said explore.org naturalist Mike Fitz, who started the contest when he was a ranger at Katmai.

This year's sockeye run has been abundant, so voters can expect some especially corpulent contestants.

The 12 bears — which ones will be anounced Monday — will be featured in the single-elimination, bracket-style tournament. All voting is done online at www.fatbearweek.org, with the winner declared Sept. 30.

The first round features eight bears squaring off in four separate contests to advance to the second round. Four bears receive first-round byes.

There are about 2,200 brown bears within Katmai, a 6,562-square-mile (16,997-square-kilometer) park located on the Alaska Peninsula, which extends from the state’s southwest corner toward the Aleutian Islands. To be featured in the contest, the bears must frequent the area of the main Brooks Camp.

They don’t, though that would be a monumental task. Male brown bears at Katmai weigh about 700 to 900 pounds (318 kg to 408 kg) mid-summer and can bloat to over a 1,000 pounds (454 kg) by September or October, thanks to successful foraging.

A 1,200-pound (544 kg) male bear isn’t unusual at Katmai. Others have been estimated to be about 1,400 pounds (635 kg). Females are about half to two-thirds the size of adult males.

Brooks Falls is a famous spot where brown bears are known for standing in the middle of the river and snagging salmon out of the air as the fish try to jump upstream to get to their spawning ground.