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 782

Study Type: 

wild

Location: 

Nantucket Sound

Target catch: 

Loligo squid

Effect on bycatch species: 

The two extensions were able to remove scup at mean rates of 86-100% , although small (<10 cm FL) scup were not excluded. No difference in removal rates between the two extensions.

Effect on target catch: 

The vee excluder removed more squid (53-69%) from the net compared to the ring excluder (7-58%).

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Field Study 736

Study Type: 

wild

Location: 

Isle of Man

Target catch: 

Queen scallop

Effect on bycatch species: 

There was no significant difference in the abundance of bycatch between the traditional and new "Newhaven" dredge design.

Effect on target catch: 

The new "Newhaven" dredge caught significantly more queen scallops than the traditional dredge.

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Field Study 644

Study Type: 

wild

Location: 

Massachusettes Bay

Target catch: 

Silver hake

Effect on bycatch species: 

Over 88% of spiny dogfish were excluded by the grate regardless of color or gear configuration.

Effect on target catch: 

Within typical commercial quantities

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Field Study 641

Study Type: 

wild

Location: 

Gulf of Maine

Target catch: 

Pink shrimp (Pandalus borealis)

Effect on bycatch species: 

Reduced the bycatch of silver hake, red hake, American plaice and witch flounder compared to the Nordmore Grid and allowed larger fish to escape

Effect on target catch: 

The catch and size of pink shrimp was not significantly different between the Nordmore Grid and Rope Grid

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Field Study 615

Study Type: 

wild

Location: 

New South Wales Australia

Target catch: 

Prawns

Effect on bycatch species: 

The Nordmore-grid codend caught 50% fewer yellowfin bream than the radial escape section net and 55% fewer than the control net. Both trial codends significantly reduced the predicted mean weight (36% Nordmore-grid and 74.3% radial escape section) and n

Effect on target catch: 

The codend with a radial escape section and the simplified Nordmore-grid retained fewer school prawns by weight 11.5% and 4.6% resepectively, compared to the control net.

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Field Study 609

Study Type: 

wild

Location: 

Gulf of California

Target catch: 

Shrimp

Effect on bycatch species: 

The industrial version of the prototype reduced bycatch-to-shrimp ratios from 20-50% and the artisanal version also reduced the bycatch-to-shrimp ratios.

Effect on target catch: 

The industrial prototype increased target catch efficiency

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