Circle hooks

A circular hook design in which the point of the hook is perpendicular to the hook shank. Circle hooks are used widely in many recreational and commercial fisheries and recently have been shown to reduce both the hooking rate and the mortality of turtles that are hooked on pelagic longline gear. As a result of several successful field trials (Bolten and Bjorndal, 2005; Watson et al., 2005), these hooks are becoming increasingly used in longline fisheries.

Are circle hooks effective in reducing incidental captures of loggerhead sea turtles in a Mediterranean longline fishery?

Study Type: 

wild

Location: 

Strait of Sicily

Target catch: 

Swordfish

Effect on bycatch species: 

Circle hooks reduced the incidental capture of immature sea turtles

Effect on target catch: 

Circle hooks did not affect catch rates or the size of the targeted catch

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Study Type: 

wild

Location: 

off Hawaii

Target catch: 

Swordfish

Effect on bycatch species: 

Highly significant reduction in the proportion of turtles that swallowed hooks

Effect on target catch: 

Swordfish catch increased by 16%, tuna catch decreased by 50%, and mahi-mahi, opah, and wahoo catch decreased by 34%

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Study Type: 

wild

Location: 

off Hawaii

Target catch: 

Swordfish

Effect on bycatch species: 

Leatherback turtle capture rates declined by 83% and loggerhead capture rates declined by 90%

Effect on target catch: 

Swordfish catch increased by 16%, tuna catch decreased by 50%, and mahi-mahi, opah, and wahoo catch decreased by 34%

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Experiment to Evaluate Gear Modification on Rates of Sea Turtle Bycatch in the Swordfish Longline Fishery in the Azores Phase 4

Study Type: 

wild

Location: 

Azores

Target catch: 

Swordfish and blue shark

Effect on bycatch species: 

Non-offset 16/0 and 18/0 circle hooks caught fewer turtles than Japanese tuna hook. Non-offset 18/0 circle hooks caught fewer turtles than non-offset 16/0

Effect on target catch: 

There was no significant difference in the number of blue sharks caught on non-offset 16/0 and 18/0 circle hooks .

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Experiment to Evaluate Gear Modification on Rates of Sea Turtle Bycatch in the Swordfish Longline Fishery in the Azores Phase 3

Study Type: 

wild

Location: 

Azores

Target catch: 

Swordfish and blue shark

Effect on bycatch species: 

Decreased throat hooking

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Experiment to evaluate gear modification on rates of sea turtle bycatch in the swordfish longline fishery in the Azores phase 2

Study Type: 

wild

Location: 

Azores

Target catch: 

Swordfish and blue shark

Effect on bycatch species: 

Did not reduce bycatch; reduced rate of throat hooking

Effect on target catch: 

Increased blue shark catch when compared to J hooks

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Experiments in the western Atlantic Northeast Distant Waters to evaluate sea turtle mitigation measures in the pelagic longline fishery. Report on experiments conducted in 2001-2003.

Study Type: 

wild

Location: 

Atlantic

Target catch: 

Swordfish and tuna

Effect on bycatch species: 

Reduced bycatch

Effect on target catch: 

Effect varied by species and by bait

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Reduction technique: 

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Fishing methods to reduce sea turtle mortality associated with pelagic longlines

Study Type: 

wild

Location: 

United States

Target catch: 

Swordfish

Effect on bycatch species: 

Reduced bycatch and hook ingestion

Effect on target catch: 

No negative effect

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