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.

Field Study 355

Study Type: 

wild

Location: 

Northern Australia

Target catch: 

Prawns

Effect on bycatch species: 

JT 1 design did not prevent capture of large sharks and rays

Effect on target catch: 

Caught 6.6% more tiger prawns and 10.5% more endeavour prawns than standard net

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Field Study 354

Study Type: 

wild

Location: 

Northern Australia

Target catch: 

Prawns

Effect on bycatch species: 

JT 2 design did not prevent capture of sea turtles

Effect on target catch: 

Caught 5.2% more tiger prawns and 6.9% more endeavour prawns than standard net

Article: 

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Field Study 353

Study Type: 

wild

Location: 

Northern Australia

Target catch: 

Prawns

Effect on bycatch species: 

JT 1 design did not prevent capture of sea turtles

Effect on target catch: 

Caught 6.6% more tiger prawns and 10.5% more endeavour prawns than standard net

Article: 

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Reduction technique: 

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Field Study 345

Study Type: 

wild

Location: 

New South Whales, Australia

Target catch: 

School prawn

Effect on bycatch species: 

Retained fewer fish

Effect on target catch: 

In experiment 2, where a trawler was placed in front of the mouth of the net, the selection range of school prawns was incrementally smaller from the 1-m square-mesh codend to the 3-m square mesh codend compared to the diamond mesh codend and school praw

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Field Study 342

Study Type: 

wild

Location: 

Alaska

Target catch: 

Groundfish

Effect on bycatch species: 

94% of Pacific halibut escaped when the ridgid grate was used

Effect on target catch: 

72% of Dover sole, 67% of rex sole and 79% of flathead sole were retained

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Field Study 330

Study Type: 

wild

Location: 

Alaska, Bering Sea

Target catch: 

walleye pollock (Theragra chalcogramma)

Effect on bycatch species: 

Streamers reduced seabird strikes on two cable types

Effect on target catch: 

none

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Field Study 326

Study Type: 

wild

Location: 

Northern Australia

Target catch: 

Prawns

Effect on bycatch species: 

Little effect

Effect on target catch: 

Little effect

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Field Study 325

Study Type: 

wild

Location: 

Northern Australia

Target catch: 

Prawns

Effect on bycatch species: 

Downward facing TEDs reduced large sponge catches by 95.9%

Effect on target catch: 

Reduced the proportion of soft and damaged prawns by 63.2% and reduced catches of tiger prawns by 6.3%

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