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.

A simple technical measure to reduce bycatch and discard of skates and sharks in mixed-species bottom-trawl fisheries

Study Type: 

wild

Location: 

Minch and Stanton Banks

Target catch: 

Whitefish

Effect on bycatch species: 

Removing the 'tickler' chain resulted in decreased catches of sharks and skates

Effect on target catch: 

Catch rates for flatfish, haddock and whiting did not differ. Larger anglerfish were caught without the 'tickler' in place

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Development and observations of spiny dogfish Squalus acanthias reduction device in a raised footrope silver hake Merluccius bilinearis trawl

Study Type: 

wild

Location: 

Massachusettes Bay

Target catch: 

Silver hake

Effect on bycatch species: 

There were no observed differences in the behavior of spiny dogfish between gear configurations or grate colors.

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Field Study 844

Study Type: 

wild

Location: 

Venezuela

Target catch: 

shrimp

Effect on bycatch species: 

Decrease of 26-32%

Effect on target catch: 

Maintained or increased

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Field Study 823

Study Type: 

summary

Target catch: 

Nephrops

Effect on bycatch species: 

Square mesh panels, combined with guiding panels, were effective for retaining marketable bycatch and reducing discards

Effect on target catch: 

Maintains target catch levels.

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Field Study 804

Study Type: 

wild

Location: 

North Sea

Target catch: 

Plaice and sole

Effect on bycatch species: 

Significantly fewer invertebrates; no difference in undersized plaice; significantly fewer undersized sole

Effect on target catch: 

Significantly fewer plaice and sole

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Field Study 791

Study Type: 

wild

Location: 

Gulf of Maine

Target catch: 

Pink shrimp

Effect on bycatch species: 

Atlantic herring bycatch decreased 86.6%; flounder spp. bycatch increased by <3%

Effect on target catch: 

Increased 13.5%

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