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.

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Study Type: 

Study in the lab

Location: 

Melbourne Zoo, Australia

Target catch: 

N/A

Effect on bycatch species: 

Orange colored monofilament resulted in lower collision rates with a gillnet mimic versus green and clear monofilament

Effect on target catch: 

Not tested

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Omura Bay, Japan

Target catch: 

Not studied

Effect on bycatch species: 

Initially, pinger use decreased porpoise encounter rates with gillnets. However, this effect decreased over time but was effective later after temporary cessation of pinger use.

Effect on target catch: 

Not tested

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

San Jose, Salaverry, Ancon, Peru

Target catch: 

Elasmobranchs, tuna, dolphinfish

Effect on bycatch species: 

Bycatch probability per set was reduced by up to 74.4% for sea turtles and 70.8 for small cetaceans in comparison to non-illuminated nets. For seabirds, nominal BPUE decreased by 84% in the presence of LEDs.

Effect on target catch: 

No effect

Article: 

Study Type: 

Summary study

Location: 

Northwest Atlantic

Target catch: 

N/A

Effect on bycatch species: 

N/A

Effect on target catch: 

The northwest Atlantic population of leatherback turtles faces potentially common widespread threats from predation and fishing gear across its range.

Article: 

Bycatch species: 

Fishing Gear: 

Study Type: 

Summary study

Location: 

Cornwall

Target catch: 

Hake

Effect on bycatch species: 

Only the AIRMAR pinger worked satisfactorily

Effect on target catch: 

N/A

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Bay of Fundy

Target catch: 

Atlantic cod, Atlantic herring, pollock

Effect on bycatch species: 

There was a 77% reduction in porpoise bycatch when acoustic alarms were used.

Effect on target catch: 

There was no significant difference in catch rates when alarms were and were not used.

Article: 

Bycatch species: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Ireland

Target catch: 

none

Effect on bycatch species: 

CETASAVER and Dolphin Deterrent Device resulted in mild responses by dolphins. BIM pingers elicited no response.

Effect on target catch: 

N/A

Article: 

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