Because there is a river that passes by this town. In the past, there were many fishermen, and a lot of dishes were prepared from fish. During this event, a competition is held, preparing a speciality called fish stew, and initially, it was the highlight of the event. Now, the competition is still held but so many other things are added too :)
What an interesting history. I hope the fish stew tradition is kept. Feels like it's important history.