Fish escape windows/separator devices

These devices are incorporated into trawl nets and are designed to give finfish openings for escape while retaining target shrimp species in the rear (codend) of the net. Examples include “skylights” which consist of a mesh opening located at the top of the codend. ”Skylights” can be combined with guiding funnels that create visual and tactile stimuli to direct finfish towards the “skylight” escape sections. A different but similar type of design is the fisheye (including Gulf and yarrow fisheyes and bigeyes) which are openings typically forming a rigid frame constructed of aluminum or steel rods and placed along the top center portion of the codend. These devices create and area of reduced water flow immediately below them that fish can use for swimming behavioral orientation and escape.

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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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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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 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%

Article: 

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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

Study Type: 

wild

Location: 

Western and Central Pacific Ocean

Target catch: 

Tuna

Effect on bycatch species: 

Only two out of 105 silky sharks were able to escape through the release panel. No finfish species escaped.

Effect on target catch: 

None reported

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Field Study 586

Study Type: 

wild

Location: 

Mid Atlantic Bight

Target catch: 

Longfin squid

Effect on bycatch species: 

The square-mesh escape panel significantly reduced the average catches of scup and black sea bass. The panel also reduced catches of sublegal-size scup and black sea bass.

Effect on target catch: 

Longfin squid catch was reduced by 88% and 84% in numbers and weight respectively.

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Field Study 555

Study Type: 

wild

Location: 

Northern Australia

Target catch: 

Prawns

Effect on bycatch species: 

Reduced the number of sharks and rays by 35% when the Popeye Fishbox was placed 70 meshes from the codend draw strings and by 27% when it was placed 100 meshes from the codend draw strings

Effect on target catch: 

Did not significantly reduce the catch of prawns

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