In the Eastern Pacific, the species commonly affected by incidental capture in longlines and gillnets are the leatherbacks, green turtles from the Eastern Pacific, olive ridleys and loggerheads.
The first three species reproduce and feed in the Exclusive Economic Zones of Latin American countries. Loggerheads travel from Australia and Polynesia to feed in the nutrient rich waters of the Humboldt stream along the coast of Chile and Peru.
The recovery of marine turtle populations is part of our shared commitment to restore and maintain marine biodiversity and resources for the generations to come.
Marine turtles play ecological roles in the marine food web and their decline affects the local economies of coastal communities that depend on them such as in Playa Grande, Costa Rica, where leatherback tourism is a major source of revenue.
Longlines and marine turtle bycatch
A recent, global estimate of the effect of fisheries on marine turtles suggests that some 260,000 loggerheads and 50,000 leatherbacks are captured incidentally by longlines each year, a proportion of which dies as a consequence.
This rate of loss of individuals is not sustainable to the sea turtle population affected.
The precipitous decline of the Eastern Pacific leatherbacks has been attributed in part to bycatch mortality. The main targets of longlines in the Eastern Pacific are tuna, sharks and mahi mahi. Industrial longlines can be as long as 50 to 70 nautical miles and carry more than 10,000 hooks. Artisanal longlines are usually some 0.5 to 2 km long and carry several hundred hooks. Typically, the hook of choice is a medium sized 'j-hook' baited with squid or fish.
The circle hook solution
Studies by NOAA/NMFS in the Atlantic first revealed that large circle hooks in longlines reduce marine turtle bycatch by more than 67%. Other factors that affect the probability of catching marine turtles include the type of bait, time of the day and water temperature of the fishery, among others.
In addition, large circle hooks tend to catch the turtle in the mouth region, where unhooking is easier for the fishermen. Hookings in the throat or esophagus are rare. Leatherbacks are less likely to be caught by hooks on the flipper or armpit when they swim into a line with circle than with j-hooks.
Hooks that are good for everyone?
In general, circle hooks do not reduce the catch of target species. In addition, since fish are hooked in the mouth region, and much less so in the esophagus, the catch is less lethal and the fish remain fresh for a longer period of time. This in turn, results in better market prices for the catch.
In 2003, the Inter-American Tropical Tuna Commission (IATTC) launched an initiative among its member states to run experiments toward the replacement of j-hooks with circle hooks in longlines of the Eastern Pacific. WWF is a committed co-sponsor of this initiative and has provided funds, technical and administrative expertise toward its implementation.
The first round of experiments with the artisanal longline fleet of Ecuador was completed in 2004. Workshops with fisher folk were initiated in Colombia, Guatemala and Mexico. The program will include in the near future El Salvador, Nicaragua, Costa Rica, Panama, Peru and Chile. The workshops include training in handling, recovery and release of sea turtles, after hookings or entanglements.
||Establishment of an alliance for implementation of the gear replacement in each country, including government agencies, fisheries industry and local NGOs.
||Facilitation of horizontal transfer of experiences with circle hooks between fisher folk.
|| Experimental introduction of circle hooks and training to reduce post-capture mortality – fishermen can opt to move back to their j-hooks, if they are not satisfied with the performance of the circle hooks.
||Facilitation of availability of circle hooks in the national market.
||Passing of legally binding regulations to replace j-hooks with circle hooks in the longline industry.
|| Further training and follow-up as necessary.
Longline bycatch is one important contributor to the offshore mortality of marine turtles. Gillnets, however, are a common and widespread source of additional mortality, which has not been quantified or otherwise systematized so far. The quest for creative solutions to significantly reduce sea turtle mortality associated to gillnets and other fishing gear lies at the forefront of WWF's subsequent plans. SMARTGEAR
is a research fund supported by WWF, targeted toward innovative fisher folk who want to contribute technical solutions to marine turtle conservation.