The gillnet catches fish which try to pass through it by snagging on the gill covers. Thus trapped, the fish can neither advance through the net nor retreat. Uses a system of nets with floats and weights. The nets are anchored to the sea floor and allowed to float at the surface

A trammel

A trammel is a fishing net with three layers of netting that is used to entangle fish or crustacea.[31] A slack central layer with a small mesh is sandwiched between two taut outer layers with a much larger mesh. The net is kept vertical by the floats on the headrope and weights on the bottomrope.