Interactions of Fisheries in the Eastern Pacific Ocean and Marine Turtles

Citation
IATTC (2006) Interactions of Fisheries in the Eastern Pacific Ocean and Marine Turtles. WCPFC, Manila, Philippines
Abstract

Sea turtles are caught on longlines when they take the bait on hooks, are snagged accidentally by hooks, or are entangled in the lines. Estimates of incidental mortality of turtles due to longline and gillnet fishing are few. At the 4th meeting of the IATTC Working Group on Bycatch in January 2004, it was reported that 166 leatherback (Dermochelys coriacea) and 6,000 other turtle species, mostly olive Ridley (Lepidochelys olivacea), were incidentally caught by Japan's longline fishery in the EPO during 2000, and that, of these, 25 and 3,000, respectively, were dead. The mortality rates due to longlining in the EPO are likely to be similar for other fleets targeting bigeye tuna, and possibly greater for those that set lines at shallower depths for albacore and swordfish. About 23 million of the 200 million hooks set each year in the EPO by distant-water longline vessels target swordfish with shallow longlines.
In addition, there is a sizeable fleet of locally-based longline vessels that fish for tunas and billfishes in the EPO. During 2005, the IATTC staff and some other organizations rendered advice and assistance to the governments of several Latin American nations bordering on the Pacific Ocean to reduce the mortality of sea turtles caused by the artisanal longline fishery for tunas and other species. Additional information on this program can be found in Section 8.2. Sea turtles are occasionally caught in purse seines in the EPO tuna fishery. Most interactions occur when the turtles associate with floating objects, and are captured when the object is encircled. In other cases, nets set around unassociated schools of tunas or schools associated with dolphins may capture sea turtles that happen to be at that location. The olive Ridley turtle is, by far, the species of sea turtle taken most often by purse seiners. It is followed by black or green sea turtles (Chelonia agassizii), and, very occasionally, by loggerhead (Caretta caretta) and hawksbill (Eretmochelys imbricata) turtles. Only one mortality of a leatherback turtle has been recorded during the 10 years that IATTC observers have been recording this information. Some of the turtles are unidentified because they were too far from the vessel or it was too dark for the observer to identify them. Sea turtles, at times, become entangled in the webbing under fish aggregating devices (FADs) and drown. In some cases, they are entangled by the fishing gear and may be injured or killed.