Development and Implementation of Bluefin Tuna (Thunnus thynnus) Bycatch Mitigation Measures in the Gulf of Mexico Yellowfin Tuna Pelagic Longline Fishery

Research was conducted in 2008 -2010 by the Engineering and Harvesting Branch of NOAA Fisheries, Southeast Fisheries Science Center, Mississippi Laboratories to evaluate the efficacy of a new 16/0 “weak” circle hook design in reducing the bycatch of bluefin tuna in the Gulf of Mexico yellowfin tuna fishery.  Six commercial vessels completed 311 pelagic longline sets.  Experimental hooks and standard 16/0 circle hooks were alternated on the longline, with a total of 198,606 hooks set.  A total of 33 bluefin were caught during the experiment, of which 10 were caught on the experimental hook (56.5% reduction).  The difference in bluefin catch was statistically significant.  Vessels caught a total of 2,065 yellowfin tuna.  The difference in the yellowfin catch rate for standard and experimental hooks was not significant.