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.

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Study Type: 

Field study in the wild

Location: 

Azores

Target catch: 

Swordfish and blue shark

Effect on bycatch species: 

There was no significant difference in the number of loggerhead sea turtles caught in the Azores longline swordfish and blue shark fishery between straight 16/0, offset 16/0, and offset 18/0 circle hooks.

Effect on target catch: 

Straight 16/0 circle hooks caught the most blue sharks in the Azores longline swordfish and blue shark fishery, followed by offset 18/0 circle hooks. Offset 16/0 circle hooks caught the fewest blue sharks.

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Study Type: 

Field study in the wild

Location: 

Western North Atlantic

Target catch: 

Swordfish and tuna

Effect on bycatch species: 

Circle hooks decreased loggerhead and leatherback catch; even more effective for loggerheads when combined with mackerel bait

Effect on target catch: 

Circle hooks combined with mackerel bait increased swordfish catch by weight. With squid, decreased swordfish catch, increased bluefin and albacore tuna catch. Mackerel bait decreased bigeye and albacore tuna catch.

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Study Type: 

Field study in the wild

Location: 

Southwest Atlantic

Target catch: 

Tuna

Effect on bycatch species: 

American style longlines - no significant difference in catch rates for blue or porbeagle sharks, seabirds or sea turtles. Spanish style longline - significant decrease in pelagic stingray catch rates on circle hooks, no significant differences in catch

Effect on target catch: 

Albacore catches increased with circle hooks on both types of longline. Shortfin mako shark catch rates increased with circle hooks on the American style longlines.

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Study Type: 

Field study in the wild

Location: 

Central Mediterranean Sea

Target catch: 

swordfish

Effect on bycatch species: 

Circle hooks captured fewer (2) loggerheads compared to 2J hooks (9)

Effect on target catch: 

16/0 hooks resulted in a non-statistically significant decrease in catchability compared to size 2 J hooks, but statistically significant decrease compared to size 4 and 5 J hooks

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Study Type: 

Field study in the wild

Location: 

Eastern Pacific Ocean

Target catch: 

Billfish and tuna

Effect on bycatch species: 

Significant differences were found between J4 and C15 and between J4 and C18.

Effect on target catch: 

Significant differences between catch rates were only found between the J-4 and C18 hooks. Large circle hooks (C18) had the lowest catch rates for tunas and small circle hooks (C15) had the lowest catch rates for billfish

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Study Type: 

Field study in the wild

Location: 

Pacific Ocean

Target catch: 

Tuna

Effect on bycatch species: 

Blue and oceanic whitetip shark bycatch increased.

Effect on target catch: 

Tuna catches were significantly higher, but lengths for bigeye and skipjack were smaller; shortbill spearfish and striped marlin catch was lower; no difference in swordfish catch rates, but lengths were greater

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