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.

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Tests of artificial light for bycatch reduction in an ocean shrimp (Pandalus jordani) trawl: Strong but opposite effects at the footrope and near the bycatch reduction device

Study Type: 

Field study in the wild

Location: 

Oregon, USA

Target catch: 

Ocean shrimp

Effect on bycatch species: 

Reduced

Effect on target catch: 

Maintained catch levles

Article: 

Tests of artificial light for bycatch reduction in an ocean shrimp (Pandalus jordani) trawl: Strong but opposite effects at the footrope and near the bycatch reduction device

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Deep-sea benthic habitats and the impacts of trawling on them in the offshore Greenland halibut fishery, Davis Strait, west Greenland

Study Type: 

Field study in the wild

Location: 

Greenland

Target catch: 

Greenland halibut (Reinhardtius hippoglossoides)

Effect on bycatch species: 

Disturbance to invertebrate communities

Effect on target catch: 

Not reported

Article: 

Deep-sea benthic habitats and the impacts of trawling on them in the offshore Greenland halibut fishery, Davis Strait, west Greenland.

Bycatch species: 

Fishing Gear: 

Kon's Covered Fisheye BRD Trial Report

Study Type: 

Field study in the wild

Location: 

North Coast, Australia

Target catch: 

Prawns: White Banana (Fenneropenaeus merguiensis), Red-legged Banana (F. indicus), Brown Tiger (Penaeus esculentus), Grooved Tiger (P. semisulcatus), Blue Endeavour (Metapenaeus endeavouri), and Red Endeavour (M. ensis)

Effect on bycatch species: 

Reduced bycatch if small individuals by 37.6%

Effect on target catch: 

Increased by .05%

Article: 

Kon's Covered Fisheyes BRD Trial Report

Bycatch species: 

Reduction technique: 

Fishing Gear: 

The efficiency of sieve‐panels for bycatch separation in Nephrops trawls

Study Type: 

Field study in the wild

Location: 

Skagerrak, Norway

Target catch: 

Norway lobster (Nephrops norvegicus)

Effect on bycatch species: 

Bycatch of roundfish and flatfish was low

Effect on target catch: 

Optimal catch size of large Nephrops was too low for commercial use

Article: 

The efficiency of sieve‐panels for bycatch separation in Nephrops trawls

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Using vertical distribution to separate fish from crustaceans in a mixed species trawl fishery

Study Type: 

Field study in the wild

Location: 

Skagerrak, Norway

Target catch: 

Norway lobster (Nephrops norvegicus)

Effect on bycatch species: 

The majority of fish were separated successfully into the upper compartment

Effect on target catch: 

Not tested

Article: 

Using vertical distribution to separate fish from crustaceans in a mixed species trawl fishery

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Shorter trawls improve size selection of northern shrimp

Study Type: 

Field study in the wild

Location: 

Skagerrak, Norway

Target catch: 

Northern shrimp (Pandalus borealis)

Effect on bycatch species: 

Bycatch of Norway pout was slightly reduced in the shorter trawl.

Effect on target catch: 

The trawls fished shrimp above 19 mm carapace length equally, while catch rates of shrimp below 15.5–16 mm carapace length in the shorter trawl were more than halved.

Article: 

Shorter trawls improve size selection of northern shrimp

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery

Study Type: 

Field study in the wild

Location: 

Bay of Biscay

Target catch: 

hake (Merluccius merluccius), megrim (Lepidorhombus, spp.), and anglerfish (Lophius spp.)

Effect on bycatch species: 

Increasing panel size increased escapes of blue whiting

Effect on target catch: 

Placing the square mesh panel lower in. the trawl net panel increased escape of undersized hake

Article: 

Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Escapement patterns of red mullet, sole, horse mackerel and hake facing two trawl selective devices

Study Type: 

Field study in the wild

Location: 

Bay of Biscay

Target catch: 

Norway lobster (Nephrops norvegicus), demersal fish

Effect on bycatch species: 

Horse mackerel and hake escaped through the two devices tested. More sole were caught in the SMBRD than with standard gear. T90 mesh resulted in increased escape of red mullet.

Effect on target catch: 

Generally unaffected

Bycatch species: 

Reduction technique: 

Fishing Gear: 

The efficacy of illumination to reduce bycatch of eulachon and groundfishes before trawl capture in the eastern North Pacific ocean shrimp fishery

Study Type: 

Field study in the wild

Location: 

Oregon, USA

Target catch: 

Ocean shrimp (Pandalus jordani)

Effect on bycatch species: 

Illumination reduced bycatch of eulachon (Thaleichthys pacificus) and yellowtail rockfish (Sebastes flavidus), but did not result in significant changes in the bycatch of other rockfish (Sebastes spp.) and flatfish

Effect on target catch: 

No change in average catch efficiency or length-dependent catch efficiency.

Article: 

The efficacy of illumination to reduce bycatch of eulachon and groundfishes before trawl capture in the eastern North Pacific ocean shrimp fishery

Bycatch species: 

Reduction technique: 

Fishing Gear: 

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