Gillnets and similar nets are fish nets standing upright in the water. The gillnets and similar nets are held open by a floating headline and a weighted underline. Standing nets can be used both high in the water column and on the seabed, depending on the target species. At a gillnet the fish gets caught behind the gillets when it does not fit through the meshes and wants to swim back. Gillnets and similar nets cause virtually no soil damage. Gillnets are also selective. Some gillnets and similar nets presents danger to porpoises and dolphins. Lost nets can also cause damage (ghostfishing). Related technique: tangle net; A tangle net consists of a loose network of light and supple yarn in which fish and crustaceans become confused.