The game has a very complex fighting system, so when creatures fight, sometimes they fall down, after a big hit with a hammer, or getting knocked unconscious. If they are not fatally wounded, they will get back up. There's a lot of actions that happen inside the game, but not always in the 'correct' context, as the game is still in development.
And somewhere on the internet, there was a screenshot with combat log showing:
The Carp attacks the Miner but She jumps away!
The Carp stands up.
So carps were already a challenge, and then you read they can stand up!? Imagine the terror of an army of strong beasts marching down to your fort from a nearby river.
There were many bugs in the game, if you like rabbitholes, this is a good one.
He probably paid some fishing tourist shop to get him to just the right place so he could hook it and pull it in. That pic cost him money, and it's really important to him.