I call it the 'Weir'. Yesterday, I pulled four fat fish from the pit without firing a single arrow. The wolves can keep the forests; I own the river now.
Construct two diagonal walls extending from the shore into the water, forming a "V" shape. The wide opening of the "V" should face upstream or toward the main body of water. The narrow point (the apex) should be just 1-2 blocks wide. vintagestory weir trap
Best if you want to place a piece of paper in a chest near a river on a server to teach new players organically. I call it the 'Weir'
These traps can catch not only fish but also the occasional sea shell or trinket that drifts in. I call it the 'Weir'. Yesterday