World Status, Exploitation and Trade - WIDECAST

INTRODUCTIONThe next longest record of an egg harvest dates back to 1927 from the TurtleIslands off Sarawak and has been discussed many times (see Malaysia sectionfor references). Over a period of 58 years, the egg harvest has declinedfrom between two and three million to about 140 000. The level of harvestwas estimated to be between 90 and 100% prior to 1978, but since then up to50% of the eggs have been transplanted to a hatchery and the hatchlingsreleased. The harvest on these islands is known to date back at least tothe mid-19th century, but the intensity is not known, although it is thoughtto have been high. Between 1947 and 1985 the egg harvest, and by inferencethe nesting population, declined by an average of 7% a year.Malaysian turtle eggs have also been harvested on some offshore islands offSabah. Records date back to 1947, but are considered unreliable prior to1965. From then until 1985, the egg yield declined by an average of 3.4% ayear, although since 1973 nearly all of the eggs have been transferred tohatcheries rather than being sold.Polunin and Nuitja (1982) assessed historical data on egg yields from twolocalities in Thailand and three in Indonesia, demonstrating declines at allfive, though the time spans were too short to justify statistical analysis.Egg yields from the Turtle Islands in the south-western Philippines havebeen documented intermittently since 1950, and indicate a decline.On the other side of the world, Suriname is another locality where eggcollecting ( C. mydas ) is heavy but the adults are not exploited to any greatextent. Prior to 1969, there was little protection, and Schulz (1975)estimated that the level of egg harvesting had gradually increased to about90% of all those laid. From 1970 onwards, attempts have been made to reducethe harvests, which have now fallen to about 20-60% of the totalproduction. The numbers of females nesting each year have fluctuatedconsiderably, but they appear to show some evidence of a slight increasesince 1967. Contrary to some claims, this increase should not be attributedto the undoubted improvements in the control of the egg harvest, becausefemales from eggs laid since 1970 are unlikely to have yet returned to startbreeding.Hendrickson (1958) originally pointed out, discussing C. mydas inparticular, that if each egg weighs around 35 g, and each female lays around600 eggs per season, her production would amount to some 20 kg ofprotein-rich food a season. Approximately half the body weight of a 120 kgfemale, or 60 kg, would be edible meat, so a female would have to nest inthree seasons for the weight of food provided by her eggs to equal theweight of food provided by the carcass. Hendrickson goes on to argue that,since a female may survive to lay eggs in more than three years, whereasslaughter of a female is a terminal event, utilisation of eggs would be thepreferred mode of utilisation. This conclusion assumes that almost all ofthe annual egg production could be harvested without significant damage tothe nesting population, and that remigration is a more frequent phenomenonthan has been demonstrated to date. Mrosovsky (1983) and others havestressed that egg harvesting, particularly if other egg predators arediscouraged and if eggs doomed to inundation are taken, is a far preferablestrategy to the harvesting of adult turtles, not only because it should beless damaging to the survival of the breeding population if carried out inmoderation, but also because it can result in a far higher yield of ediblematerial. However, history has shown that moderation is seldom exercised,and that prolonged egg harvests appear usually to result in substantialdeclines in the breeding populations, although the rates of decline under26