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 772

Study Type: 

wild

Location: 

Queensland, Australia

Target catch: 

Sharks

Effect on bycatch species: 

Dolphins heard the F3 pinger 45 m from the net, they could only detect the F10 pinger less than 40 m from the net

Effect on target catch: 

None reported

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Field Study 771

Study Type: 

wild

Location: 

Queensland, Australia

Target catch: 

Sharks

Effect on bycatch species: 

Humpback whales heard the F3 pinger 90 m from the net, they heard the F10 pinger was audible up to 130 m

Effect on target catch: 

None reported

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Field Study 756

Study Type: 

wild

Location: 

Cornwall

Target catch: 

None reported

Effect on bycatch species: 

There was a significant difference in the number of porpoise clicks between nets with and without pingers, but the extent of displacement could not be determined. No evidence of habituation to the pingers.

Effect on target catch: 

None reported

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Field Study 718

Study Type: 

wild

Location: 

Cornwall

Target catch: 

Monkfish

Effect on bycatch species: 

One incidentally caught harbor porpoise; significant reduction in the number of porpoise clicks at nets with pingers. Pinger effects stronger at quiet sites; no habituation observed, exclusion of porpoises following pinger use for as much as 7 hrs

Effect on target catch: 

None reported

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Field Study 711

Study Type: 

wild

Location: 

Southwest England

Target catch: 

None reported

Effect on bycatch species: 

DDD's caught significantly fewer porpoises but no significant difference in dolphin bycatch was observed

Effect on target catch: 

None reported

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Field Study 637

Study Type: 

wild

Location: 

Baja California Sur, Mexico

Target catch: 

Flatfish and elasmobranchs

Effect on bycatch species: 

Chemical light sticks reduced green turtle bycatch by 60%

Effect on target catch: 

No effect

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Field Study 635

Study Type: 

wild

Location: 

Baja California Sur, Mexico

Target catch: 

Flatfish and elasmobranchs

Effect on bycatch species: 

Reduced green turtle bycatch by 54%

Effect on target catch: 

Reduced target catch by 45% and catch value by 47%

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Field Study

Study Type: 

wild

Location: 

US Mid-Atlantic

Target catch: 

Monkfish

Effect on bycatch species: 

No effect on Atlantic sturgeon; increased common dolphin bycatch

Effect on target catch: 

Removing tie-downs decreased monkfish landings

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