What does pressing 'x' do?

[Izzy_Fleming12]

So while fishing in Stardew, I've come across something, so basically you press the x key on PC while in the fishing mini-game and your character makes this exerted kind of face. All I want to know is what it does. I've seen a lot of people use this on YouTube and I have no idea what it's for.
Anyway, Thanks :)

 

[Maher]

It ends the mini game, releasing the fish.