Apart from the traditional exploitation by indigenous communities, commercial catches of sea turtles in some areas experienced an exponential increase in the 1960s for the skin and carapace, leading some populations to the point of extinction. For example, in Mexico, sea turtle captures increased from 500 tonnes (about 6 000 individuals) in the 1950s to 14 590 tonnes (about 375 000 individuals) in 1968 (Márquez, 1990). Direct take of sea turtles was also an important commercial activity in other Caribbean states (mainly Cuba). Because of the negative impacts on the populations, which made fisheries unprofitable, Mexico introduced a total ban on sea turtles take in 1971 and the CITES listing lead to an important reduction in overall sea turtle captures (Fig. 1).
The relative importance of various sources of mortality on sea turtles varies from region to region and with populations. However, sea turtle bycatch in various fisheries is believed to have a substantial impact on sea turtle populations. Although data are scant, sea turtles are known to be taken in various types of fisheries, both coastal and offshore, especially those that use gillnets, trawls (particularly shrimp trawls), pelagic longlines, set nets and purse seines, causing concern that fisheries may represent, at least in some cases, an important cause of observed declines in sea turtle populations (FAO 2004).
Before the introduction of Turtle Excluder Devices (TEDs) in 1989, estimates indicate that the United States shrimp fleet alone caught over 47 000 sea turtles each year (FAO 2004). Recent estimates of sea turtle captures of loggerhead and leatherback sea turtles in the longline fisheries worldwide show that about 200 000 loggerheads and 50 000 leatherbacks might have been incidentally caught in 2 000 (Lewison et al. 2004). These two species have experienced a sharp decline in the Pacific and the present level of mortality is believed to be unsustainable and could result in the extinction of the above populations within a few years.
Within the context of implementing responsible fisheries, reducing impacts on non-target species - particularly on vulnerable, long-lived species such as sharks, seabirds and sea turtles - is now a policy for many States, as well as for an increasing number of regional and subregional fisheries management organizations. The reduction of discards and environmental impacts is likewise a priority activity for FAO where it is specifically addressed in the work plan under the title "Reduction of discards and environmental impact from fisheries".
While there is an urgent need to reduce any type of mortality, at least for some sea turtle populations, implementing appropriate management measures is characterized by multiple challenges. These are related to the lack of sound scientific advice, mainly because of lack of data on non-commercial species, the need of minimizing negative impacts on peoples' livelihoods, the lack of appropriate institutional frameworks at the national, regional and international levels and the seemingly contradictory objectives of environmental sustainability versus poverty alleviation, just to mention a few.
Management measures that may be appropriate for reducing sea turtle mortality due to fisheries include technical measures, input and output controls and incentive-aligning strategies. Technical measures that are thought or have proven to be efficient are gear modifications such as the Turtle Excluder Devices (TEDs) in trawl fisheries and the use of circle hooks and appropriate gear configuration in longline fisheries and area closures, in connection, for example, with seasonal sea turtle migrations. In most cases, however, these measures will be effective only if they are part of a concerted action that includes reduction of all major sources of sea turtle mortality.
Many countries have specific legislation in force to protect sea turtles but effectiveness varies from country to country. Furthermore, because most species/populations have a wide distribution, it is of critical importance that an integrated geographic framework is established for conservation policies.
International conventions exist that relate directly to turtle conservation, including protection of sea turtle critical habitats (e.g. the Convention on the Conservation of Migratory Species of Wild Animals or CMS) and those that relate to trade in turtle and turtle products (e.g. CITES). At the regional level, the Inter-American Convention on the Protection and Conservation of Sea Turtles (IAC) specifically addresses sea turtle mortality resulting from fisheries. A number of MOUs (Memorandum of Understanding) are being signed as part of CMS Convention. Furthermore, a number of regional fishery management bodies such the General Fisheries Commission for the Mediterranean (GFCM), the Indian Ocean Tuna Commission (IOTC), the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Inter-American Tropical Tuna Commission (IATTC) and the Western and Central Pacific Fisheries Commission (WCPFC) have begun examining sea turtle bycatch, or have even adopted measures to address bycatch as part of their overall fisheries management schemes.
The Twenty-fifth Session of the Committee on Fisheries (COFI) raised the question of sea turtles conservation and interactions with fishing operations and agreed that "while taking into consideration existing work on sea turtle interactions and conservation", a Technical Consultation should be held in Bangkok, Thailand in 2004. The FAO Fisheries Department was asked to organize the Technical Consultation with the following scope:
- review the available information on the current status of sea turtle conservation including both incidental and direct catches, their impacts on the populations and other factors affecting the mortality of sea turtles;
- review the new development of fishing gears and techniques to reduce sea turtle mortality by incidental catches and other techniques to improve sea turtle conservation;
- produce, if appropriate, guidelines to reduce sea turtle mortality in fishing operations; and
- consider desirable assistance to Members of developing countries for the conservation of sea turtles.
The Technical Consultation "Sea Turtles Conservation and Fisheries" is scheduled for 29 November-2 December 2004.
An Expert Consultation on "Interactions between Sea Turtles and Fisheries in the Ecosystem Context" (Rome, 9 to 12 March 2004) was organized by FAO to provide technical input to the Technical Consultation, including overviews of sea turtle status, fisheries impacts, possible managerial solutions, socio-economic aspects and recommendations for future work and actions.
Conservation concerns are increasingly becoming part of fisheries management. Developing fishing practices that limit negative effects on sea turtle populations is already an important endeavour of many research laboratories and fisheries administrations. There is therefore a real possibility of improving the present situation. Important challenges, however, still pave the way to ecosystem sustainability and are related to governance and to the possibility of reconciling sustainable environment with sustainable livelihoods.