Effects of circle versus J-style hooks on target and non-target species in a pelagic longline fishery

Circle hooks and J-style hooks were tested on pelagic longline vessels (US Atlantic) to determine if the use of circle hooks reduced bycatch mortality while maintaining target species catch rates.  0⁰ offset circle hooks were determined to increase the survival of bycatch species at haulback while having little impact on target species catches.  Specifically, J-style hooks had a significantly higher total overall catch rate.  Catch rates of yellowfin tuna (Thunnus albacares) in the fall were higher (significantly) for circle hooks and pelagic stingrays (Pteroplatytrygon violacea, spring caught) were the only species that had a significantly higher catch rate on J-style hooks. Circle hooks caught four times as many yellowfin tuna in the mouth compared to J-style hooks.  Yellowfin tuna and dolphinfish (Coryphaena hippurus) caught on circle hooks in the fall and spring respectively, were significantly larger than those caught on J-style hooks.  Survival rates of dolphinfish and escolar (Lepidocybium flavobrunneum) were statistically higher at haulback when circle hooks were used in the fall and spring respectively.