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Tests were conducted on tuna longline fishing vessels in the eastern Pacific Ocean to determine if the use of J (size 4.0 traditional) or circle hooks (sizes 15, 16 and 18) and different bait resulted in differences in the catch rates of target and bycatch species. No significant differences in catch rates of the target species were found between hook types. 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). The highest catch rates for tunas were found on circle hooks size 15 and for billfishes on J hooks. The largest circle hook (18) had the lowest catch rates. Squid and jack mackerel bait had the highest catch rates for tunas and other fishes, while chub mackerel bait caught the most billfish and sharks.