The most popular Gill Nets are made from 
Monofilament Nylon or Multifilament Nylon

A gill net is an upright fence of fiber netting in which the fish are caught in the meshes of the net.  Fish, of a siz for which the net is designed, swimming into the net can pass only part way through a single mesh.  When it struggles to free itself, the twine slips back of the gill cover and prevents the fish from escaping.  The fish is thus “gilled” and can neither go forward nor back.  Various sizes of mesh are used depending on the species and size of the fish to be caught.  Gill nets can be suspended at the surface, in medwater, or close to the bottom by controlling the number of buoy lines and the size and number of floats on the top or cork line and weights on the lead line.   The net may be operated as stationary or movable gear.