Gillnets

Gillnets are single, double, or triple layers of net suspended vertically in the water column. The top of the net is connected to floats (headrope), while the bottom is weighted (footrope). Adjustment of the floats and weights allows gillnets to be positioned at varying depth, depending on the target species. Gillnets are generally deployed in large numbers and trap fish either by entangling the gills or by entangling all or part of the fish body. Variation in net mesh size allows fishermen to control the size of their catch.
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<i>Set nets</i> are stationary gillnets set near the bottom or at a particular depth. A subset of set gillnets, <i> fixed nets </i> are stretched between stakes driven into the bottom in intertidal areas. In contrast, <i>drift nets</i> are unanchored and float with the current. Drift nets are mostly used near the sea surface. <i>Trammel nets</i> are multi-layered gillnets usually set near the ocean bottom. FIsh are ensnared in the middle layer, which has the finest mesh size. <i>Encircling gillnets</i> are set in a circle in shallow water. Fishers create a disturbance in the water that drives fish into the nets. Several gillnet types may be used in conjunction; combined gill-trammel nets are particularly popular.
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For more detailed information, please visit the FAO Fisheries and Aquarculture Department <a href="http://www.fao.org/fishery/geartype/107/en" target="_blank"> gillnets </a> web page.

Field Study

Study Type: 

lab

Location: 

Neeltje Jans, The Netherlands

Target catch: 

n/a

Effect on bycatch species: 

Increased distance from the alarm source and respiration

Effect on target catch: 

n/a

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Field Study 833

Study Type: 

wild

Location: 

Peru

Target catch: 

Sharks and rays

Effect on bycatch species: 

37% reduction of bycatch

Effect on target catch: 

No effect

Article: 

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Field Study 795

Study Type: 

wild

Location: 

North Sea

Target catch: 

Hake

Effect on bycatch species: 

Pingers spaced at 455 m had 0 bycatch; pingers spaced at 585 m had a bycatch rate of 0.12

Effect on target catch: 

None reported

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Field Study

Study Type: 

wild

Location: 

North Carolina

Target catch: 

Spanish mackerel

Effect on bycatch species: 

Dolphins were less likely to interact with gillnets and more likely to echolocate

Effect on target catch: 

No effect

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