World Status, Exploitation and Trade - WIDECAST

INTRODUCTIONThus, infractions of CITES certainly do occur, and the existence of CaymanTurtle Farm, and of other species of turtle traded in compliance with theCITES convention, have almost certainly been used to facilitate illegaltrade. Whether this occurs on a large enough scale to outweigh the otheradvantages of having the trade conducted in the official eye is open todebate. It is noteworthy that all of the examples quoted above only came tolight because they were recorded in CITES Annual Reports. If they had beenconducted entirely underground we might never have known about them.OTHER THREATS TO MARINE TURTLESThroughout this report, emphasis has been laid on the deliberate hunting ofsea turtles and trade in their products; however, it should be appreciatedthat other factors attributable to man's activities may have a similarlylarge, and often greater, impact on turtle populations. These factors,outlined below, include some which cause direct mortality and some causingdisturbance and disruption of nesting behaviour.Incidental catchIncidental capture of turtles during other fishing activities is possiblythe major form of direct mortality. Hillstead et al (1982) reviewedincidental capture and concluded that shrimp trawling posed the majorthreat, probably because it is usually carried out in shallow, warm seaswhich are also the feeding areas used by most sea turtle species. Turtlesare also caught on longlines, in seines and set nets. In the lattercategory, special mention should be made of large-mesh shark nets which areextensively used in the tropics. In some cases they may be set with thedual purpose of catching turtles and sharks.Coastal developmentAmongst the many effects of coastal development, disturbance of nestingbeaches is the most obvious, as humans tend to favour the same kind of sandbeaches for recreational purposes as turtles require for nesting. In somecases, the disturbance of nesting animals may be direct, where humans on thebeach at night disturb the turtles. Examples of this have been reportedfrom Malaysia and Oman. A more insidious form of disturbance is theinstallation of lights which deter females from emerging to nest anddisorientate returning females and emerging hatchlings; this topic wasreviewed by Raymond (1984). Some day-time activities, such as the erectionof umbrellas and the compaction of sand by recreational vehicles or beachcleaning machinery, for example, may increase hatchling mortality.Typically, coastal development leads to all such factors operatingsimultaneously on the nesting population in question.The spread of human settlement often increases the collection of eggs orcapture of nesting females simply as a result of improved access to thebeach. However, human settlement also brings domestic animals such as dogsand pigs which can cause heavy predation of nests (Stancyk, 1982).PollutionFrazier (1980b) reviewed the various marine pollutants which may affect seaturtles and found grounds for serious concern although little directevidence of chemical pollution. Oil spills, being particularly obvious, are43