Excluder devices

These can consist of 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. 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 (i.e. Catchpole and Revill 2007). Typically, 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 or codend. 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).

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Study Type: 

Field study in the wild

Location: 

North Coast, Australia

Target catch: 

Prawns: White Banana (Fenneropenaeus merguiensis), Red-legged Banana (F. indicus), Brown Tiger (Penaeus esculentus), Grooved Tiger (P. semisulcatus), Blue Endeavour (Metapenaeus endeavouri), and Red Endeavour (M. ensis)

Effect on bycatch species: 

Reduced bycatch if small individuals by 37.6%

Effect on target catch: 

Increased by .05%

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Skagerrak, Norway

Target catch: 

Norway lobster (Nephrops norvegicus)

Effect on bycatch species: 

Bycatch of roundfish and flatfish was low

Effect on target catch: 

Optimal catch size of large Nephrops was too low for commercial use

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Bay of Biscay

Target catch: 

hake (Merluccius merluccius), megrim (Lepidorhombus, spp.), and anglerfish (Lophius spp.)

Effect on bycatch species: 

Increasing panel size increased escapes of blue whiting

Effect on target catch: 

Placing the square mesh panel lower in. the trawl net panel increased escape of undersized hake

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Target catch: 

Demersal fish

Effect on bycatch species: 

60% of all fish escaped through the white panel

Effect on target catch: 

Not tested

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Northern Australia

Target catch: 

Tiger prawn (Penaeus semisulcatus and P. esculentus) and endeavor prawn (Metapenaus endeavouri and M. ensus)

Effect on bycatch species: 

TEDs facilitated the escape of large elasmobranchs, with bar spacing and TED orientation acting as important design factors affecting escape.

Effect on target catch: 

Not tested

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Guyana

Target catch: 

Seabob shrimp (Xiphopenaeus kroyeri)

Effect on bycatch species: 

40% decline in elasmobranch catch rate; mean size of elasmobranch captured reduced by 6.3%

Effect on target catch: 

Not tested

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Mediterranean Sea

Target catch: 

Demersal fish

Effect on bycatch species: 

Unknown (no turtles captured in either control or experimental trawls)

Effect on target catch: 

No significant loss of commercial weight of fish, similar rates of capture without any significant loss of sizes (with the exception of anglerfish), significant reduction of debris in the codend

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the 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

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

US West Coast

Target catch: 

Flatfish

Effect on bycatch species: 

83.7% (weight) and 74.3% (number) of Pacific halibut were able to escape

Effect on target catch: 

93.3% of arrowtooth flounder, 99% of Dove sole, 96.9% of petrale sole, 96.9% of shortspine thronyhead and 90% of sablefish were retained

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Bycatch species: 

Reduction technique: 

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