Sub-surface bait setting

Methods that reduce bycatch by eliminating gear sets at the ocean surface by changing the property of fishing lines so that they are less likely to catch or ensnare animals feeding at the surface or in the mid-water column. These include devices such as setting chutes that place sets below the ocean surface in longline operations where they are less prone to seabird predation, and setting gillnets below the sea surface to reduce entanglement rates of small cetaceans (Hembree and Harwood 1987). They can also be used on longline vessels to increase the speed at which baited lines get below the water’s surface where seabird predation mainly occurs (Robertson et al. 2010). Other examples include low profile line, a kind of rope linking lobster pots that might be suspended deep enough to avoid whale entanglements but with enough floatation to lie above rocky bottoms that tend to abrade them. Weighted mainlines may also increase the sinking ate of pelagic longline gear, making it less likely to capture surface-feeding seabirds (Moreno et al. 2008). Frozen bait can be thawed before it is set in the water to increase the rate at which it sinks in longline fisheries. (The sinking rate can also be increased by puncturing the swim bladder of fish bait) (Gilman et al. 2007).

Displaying 1 - 10 of 14

Study Type: 

Field study in the wild

Location: 

Bering Sea

Target catch: 

Pacific cod

Effect on bycatch species: 

Integrated weight longlines paired with streamer lines eliminated surface foraging and shearwater catch by 97%; integrated weigh longlines reduced surface forager catch rates by 91% and unweighted longlines with paired streamer by 98%

Effect on target catch: 

Target catch rates were not affected

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

South Africa EEZ

Target catch: 

Tuna and swordfish

Effect on bycatch species: 

Combination of bird-scaring lines, weighted lines, and night sets yielded zero moralities.

Effect on target catch: 

No effect

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

South Africa

Target catch: 

Tuna

Effect on bycatch species: 

1.07 birds/1000 hooks (unweighted) vs. 0.06 birds/1000 hooks (weighted)

Effect on target catch: 

No detectable affect

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Falklands

Target catch: 

Patagonian toothfish

Effect on bycatch species: 

No bycatch

Effect on target catch: 

Catch was reduced

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

South Africa

Target catch: 

Tuna

Effect on bycatch species: 

Weighted branch lines with hybrid streamer lines reduced seabird mortalities by 86% compared to unweighted branch lines.

Effect on target catch: 

No effect

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

Study Type: 

Field study in the wild

Location: 

Eastern Australia

Target catch: 

Tuna

Effect on bycatch species: 

Live bait sank more quickly than dead bait, increasing the exposure of hooks to seabirds but the sink rates of individual live bait species were very variable. With respect to dead bait, those on the 160 g leaded swivel with a distance of 2 m leader len

Effect on target catch: 

None reported

Article: 

Bycatch species: 

Reduction technique: 

Fishing Gear: 

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