Gillnetting is a common fishing method used by commercial fishermen of all the oceans and in some freshwater and estuary areas. Because gillnets can be so effective their use is closely monitored and regulated by fisheries management and enforcement agencies. Mesh size, twine strength, as well as net length and depth are all closely regulated to reduce bycatch of non-target species. Most salmon fisheries in particular have an extremely low incidence of catching non-target species.