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.

Field Study 639

Study Type: 

wild

Location: 

California

Target catch: 

White seabass

Effect on bycatch species: 

None reported

Effect on target catch: 

Circle hooks penetrated the lip more frequently (73%) than the J-hook (41%). Hook location was correlated with immediate mortality; all mortalities involved hook damage to the visceral region. A 10% post-release mortality was seen with both hook types.

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Field Study 605

Study Type: 

wild

Location: 

eastern Pacific Ocean

Target catch: 

Tuna

Effect on bycatch species: 

Significant differences between J and circle hook size 15 and between J and circle hook size 16 were found in the bycatch species group (all species grouped together). Chub mackerel bait caught the sharks.

Effect on target catch: 

No significant differences in catch rates of the target species were found between hook types. The highest catch rates for tunas were found on circle hooks size 15. Squid and jack mackerel bait had the highest catch rates for tunas.

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Field Study 574

Study Type: 

wild

Location: 

northwest Pacific Ocean

Target catch: 

Pelagic species

Effect on bycatch species: 

None reported

Effect on target catch: 

There were no significant differences in catch rates between hook types but squid bait caught significantly more blue and silky sharks and dolphinfish.

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Field Study 572

Study Type: 

wild

Location: 

Mazaltan, Mexico

Target catch: 

Pelagic species

Effect on bycatch species: 

None reported

Effect on target catch: 

Circle hooks had the highest catch rates for the principal target species, blue and striped marlin.

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Field Study 570

Study Type: 

wild

Location: 

South-western Atlantic Ocean

Target catch: 

Tuna, blue sharks, swordfish

Effect on bycatch species: 

The incidental capture of loggerhead sea turtles was reduced by 55% and for leatherback sea turtles by 65% when circle hooks were used.

Effect on target catch: 

Catch rates of targeted species including bigeye and albacore tuna and blue sharks were increased with the use of circle hooks, while no difference was found for yellowfin tuna, shortfin mako or hammerhead sharks or for dolphinfish.

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Field Study 536

Study Type: 

wild

Location: 

Hawaii

Target catch: 

Bigeye tuna

Effect on bycatch species: 

Catch rates on circle hooks were significantly lower than on Japanese style and "J" hooks for 16 and 8 species respectively. Fish length was significantly shorter for four species on Japanese style hooks and for three species on "J" hooks. Survival was

Effect on target catch: 

There were no significant differences in catch, catch rate or mean length for bigeye tunas. Survival was significantly higher for bigeye tuna caught on circle vs. Japanese style hooks.

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Fishing gear modifications to reduce elasmobranch mortality in pelagic and bottom longline fisheries off Northeast Brazil

Study Type: 

wild

Location: 

Brazil

Target catch: 

tuna (pelagic) and sharks (bottom)

Effect on bycatch species: 

CPUE was significantly higher for night, blue, silky, and oceanic whitetip sharks on circle hooks.

Effect on target catch: 

None reported for pelagic longlines. On bottom longlines, CPUE was higher for blacknose and nurse sharks and southern stingrays; no CPUE difference between hook type; more tiger and blacknose sharks were alive at haulback with circle hooks

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Field Study 367

Study Type: 

wild

Location: 

Bay of Bengal

Target catch: 

Tunas and billfish

Effect on bycatch species: 

J-hooks caught a higer percentage (74.5%) of bycatch compared to target (25.5%) species, while circle hooks caught a similar percentage of each (53.3% and 46.7% respectively). Bycatch catch rates were higher on J-hooks (5.6 individuals/1,000 hooks) than

Effect on target catch: 

Target species catch rates were higher on circle hooks (2.2 individuals/1,000 hooks) compared to J-hooks (1.9 individuals/1,000 hooks). Swordfish caught by J-hooks were slightly larger than those caught on circle hooks.

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Field Study 340

Study Type: 

wild

Location: 

US Atlantic

Target catch: 

Tuna and swordfish

Effect on bycatch species: 

Pelagic stingrays had higher catch rates on J-style hooks and survival rates of dolphinfish and escolar were higher when circle hooks were used (fall and spring respectively)

Effect on target catch: 

Catch rates of yellowfin tuna caught in the fall were higher on circle hooks. Yellowfin tuna were caught four times as often in the mouth when circle hooks were used in the fall.

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