Trawls

Trawls are cone-shaped nets with two, four, or more panels, ending in a bag. They are towed at midwater or near the bottom, and held open horizontally by heavy doors (<i>otter trawls</i>), by beams, or by the tension created by lines connecting the net to two separate vessels (<i>pair trawls</i>). The net opening is sustained vertically by floats and weights. Fish size and species is controlled by mesh size; pelagic, demersal, and benthic fish can be targeted. The recent development of trawls with large wheels (<i>rockhoppers</i>) prevents damage and tangling of nets, and has eliminated the disincentive to trawling along rugged seafloors.
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For more detailed information, please visit the FAO Fisheries and Aquaculture Department <a href="http://www.fao.org/fishery/geartype/103/en" target="_blank">trawl nets</a> web page.

Determining the safety range of electrical pulses for two benthic invertebrates: brown shrimp (Crangon crangon L.) and ragworm (Alitta virens S.)

Mitigating the bycatch of giant cuttlefish Sepia apama and blue swimmer crabs Portunus armatus in an Australian penaeid-trawl fishery

Study Type: 

wild

Location: 

Spencer Gulf

Target catch: 

King prawn

Effect on bycatch species: 

Reduced capture of giant cuttlefish and blue swimmer crabs by 30-50%

Effect on target catch: 

Catch of target species was not affected

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Testing of an industry-designed bycatch reduction device to reduce the incidental catch of Pacific halibut in a groundfish bottom trawl fishery

Study Type: 

wild

Location: 

US west coast

Target catch: 

Flatfish

Effect on bycatch species: 

83.7% (weight) and 74.3% (number) of Pacific halibut were able to escape

Effect on target catch: 

93.3% of arrowtooth flounder, 99% of Dove sole, 96.9% of petrale sole, 96.9% of shortspine thronyhead and 90% of sablefish were retained

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Initial tests of a bycatch reduction device designed to improve trawl selectivity in the west coast limited entry groundfish bottom trawl directed flatfish fishery

Study Type: 

wild

Location: 

US west coast

Target catch: 

Flatfish

Effect on bycatch species: 

72.1% of rockfish, 96.5% of roundfishes and 93.7% of Pacific halibut were able to escape

Effect on target catch: 

85.1% of flatfish were retained

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Examining the potential use of artificial illumination to enhance Chinook salmon escapement out a bycatch reduction device in a Pacific hake midwater trawl

Study Type: 

wild

Location: 

Oregon

Target catch: 

Pacific hake

Effect on bycatch species: 

Chinook were able to escape out of the escape window; Rockfish bycatch was reduced by 32.4%

Effect on target catch: 

Pacific hake continued to swim into the codend

Reduction technique: 

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Bycatch reduction devices (BRDs) to reduce the incidental catch of cuttlefish in the Spencer Gulf prawn fishery

Study Type: 

wild

Location: 

Spencer Gulf

Target catch: 

Prawn

Effect on bycatch species: 

Small and large grids reduced number and weight of cuttlefish and crabs

Effect on target catch: 

Small grid caught less prawns compared to large grid and control nets

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An assessment of bycatch reduction devices in Kuwait's shrimp trawl fishery

Study Type: 

wild

Location: 

Kuwait

Target catch: 

Shrimp

Effect on bycatch species: 

FE significantly reduced bycatch catches

Effect on target catch: 

FE significantly reduced shrimp catches

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An assessment of bycatch reduction devices in Kuwait's shrimp trawl fishery

Study Type: 

wild

Location: 

Kuwait

Target catch: 

Shrimp

Effect on bycatch species: 

SMT significantly reduced bycatch

Effect on target catch: 

SMT caught significantly larger shrimp but not significantly fewer shrimp

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An assessment of bycatch reduction devices in Kuwait's shrimp trawl fishery

Study Type: 

wild

Location: 

Kuwait

Target catch: 

Shrimp

Effect on bycatch species: 

TED use resulted in no interactions with sea turtles or large animals; did not significantly reduce bycatch catches

Effect on target catch: 

Did not significantly reduce shrimp catches

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Selective characteristics of a shark-excluding grid device in a Mediterranean trawl

Study Type: 

wild

Location: 

Tyrrhenian Sea

Target catch: 

Norway lobster (Nephrops norvegicus) and greater forkbeard (Phycis blennoides)

Effect on bycatch species: 

90 mm excluder grid did not reduce catches of blackmouth catshark (Galeus melastomus)

Effect on target catch: 

90 mm excluder grid reduced catches of greater forkbeard and to a lesser extend Norway lobster

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