FAO.org

Fishing methods range from those which require only simple gear such as spears and rakes to the use of ocean-going vessels with enormous trawls or encircling nets. Gill netting, seine netting, electric fishing and angling are probably the most common techniques used for scientific purpose and all involve fish capture. However, observation using divers, electronic fish counters or echo sounding equipment is an option. The sampling of fish populations can be very efficient in small rivers and pools, and most freshwater research has been undertaken in such habitats. Nonetheless, the larger aquatic ecosystems are invariably of great importance as fishery resources and these have received more attention in recent years.