Welcome to Fat Bear Weekat Mashable! Each fall, Katmai National Park holds a competition as Alaska’s brown bears finish fattening up for their long winter hibernation. This year, Mashable is getting in on the salmon-munching action. Check back with us all week as we follow the fat bear face-offs each day, and remember to get your votes in for each round. Happy fishing!

UPDATE: Oct. 7, 2018, 9:07 a.m. EDT What an upset! Chunk has taken down Bear 856, the most dominant bear in the Brooks River. And in a surprise to no one, Bear 747 -- a beautiful, extremely fat bear -- took Bear 719 down.

Saturday is a day of Fat Bear Week legends.

Bear 32, known appropriately as "Chunk" by his fans, is facing down Bear 856, the scarred bully of the Brooks River. Voting is open until 10:00 p.m. ET on Saturday via Katmai National Park's Facebook page.

Both bears have plumped up nicely over the course of the salmon fishing season, so this is sure to be quite the competitive matchup.

Saturday also features another serious pairing between internet fave Bear 747 and the plucky young upstart Bear 719. Voting for that head-to-head should go live at 4 p.m. ET and close at 10 p.m. ET.

Casting your vote is easy.

Just head over to Katmai's Facebook post and hit the "Like" button on the photo of the bear who looks like they've fattened up the most on a diet rich in salmon.

Friday saw many a Fat Bear Week bracket busted. Otis -- a crowd favorite and former champion -- fell to the impressively hefty Beadnose.

While Holly, a brown bear with a heart of gold who adopted an abandoned cub, couldn't cut it against Divot, a young female without any cubs to rear this year.

Bear 856 has long been one of the most dominant bears in the river.

He has chased other large bears out of his favorite fishing spots and even committed infanticide, killing one of the cubs of a female bear at the river.

Basically, he's kind of a villain, at least when you look at it through human eyes.

But in a bear's world, Bear 856 is doing everything he needs to do in order to give himself the best chance of fattening up and having a safe hibernation through the long Alaskan winter.