Excluder devices

A grid of metal bars or mesh placed usually within the neck of a trawl that has an opening for escape at either the top or bottom. Large animals that strike the bar exit through the opening, while the smaller target species pass through the bars and are captured in the net. Examples of excluder devices in trawls are the Nordmore grid, the Turtle Excluder Device (TED), and the Sea Lion Excluder Device (SLED). A sea turtle excluder chain mat is used in the Northwest Atlantic scallop dredge fishery. A new modification to pound nets may reduce sea turtle bycatch by replacing the upper two-thirds of the leader netting with vertical ropes spaced wide enough apart to let sea turtles swim through without becoming entangled (DeAlteris et al., 2005).

Mitigating the bycatch of giant cuttlefish Sepia apama and blue swimmer crabs Portunus armatus in an Australian penaeid-trawl fishery

Study Type: 

wild

Location: 

Spencer Gulf

Target catch: 

King prawn

Effect on bycatch species: 

Reduced capture of giant cuttlefish and blue swimmer crabs by 30-50%

Effect on target catch: 

Catch of target species was not affected

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Bycatch reduction devices (BRDs) to reduce the incidental catch of cuttlefish in the Spencer Gulf prawn fishery

Study Type: 

wild

Location: 

Spencer Gulf

Target catch: 

Prawn

Effect on bycatch species: 

Small and large grids reduced number and weight of cuttlefish and crabs

Effect on target catch: 

Small grid caught less prawns compared to large grid and control nets

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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: 

TED use resulted in no interactions with sea turtles or large animals; did not significantly reduce bycatch catches

Effect on target catch: 

Did not significantly reduce shrimp catches

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Seal exclusion devices in cod pots prevent seal bycatch and affect their catchability of cod

Study Type: 

wild

Location: 

Swedish coast

Target catch: 

Cod

Effect on bycatch species: 

Reduced sea bycatch to zero

Effect on target catch: 

Oval shaped SEDs and ones with larger rectangle opening increased catchability of pots

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Selective characteristics of a shark-excluding grid device in a Mediterranean trawl

Study Type: 

wild

Location: 

Tyrrhenian Sea

Target catch: 

Norway lobster (Nephrops norvegicus) and greater forkbeard (Phycis blennoides)

Effect on bycatch species: 

90 mm excluder grid did not reduce catches of blackmouth catshark (Galeus melastomus)

Effect on target catch: 

90 mm excluder grid reduced catches of greater forkbeard and to a lesser extend Norway lobster

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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

Study Type: 

wild

Location: 

Lake Opinicon, Canada

Target catch: 

sunfish, bullheads, yellow perch, rock bass, black crappie

Effect on bycatch species: 

Significantly reduced turtle catches

Effect on target catch: 

No effect

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Field Study

Study Type: 

wild

Location: 

Missouri

Target catch: 

Fish

Effect on bycatch species: 

Significantly reduced the incidental capture of turtles

Effect on target catch: 

Did not significantly affect the quantity of fish caught

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Field Study

Study Type: 

wild

Location: 

Missouri

Target catch: 

Flathead catfish

Effect on bycatch species: 

Chimney-net design significantly reduced (84%) the bycatch of turtles

Effect on target catch: 

Chimney-net design did not reduce the number of average size of flathead catfish

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