The Agriculture, Fisheries and Conservation Department (AFCD), chose to remove the 100-odd eggs, which resemble leathery ping-pong balls, from their natural nest on the beach and incubate them artificially. This virtually guaranteed that the highest possible number of the species - protected by local laws and listed on the Convention on International Trade in Endangered Species (CITES) - would hatch. But will they return?

Artificial incubation is a controversial issue among conservationists. The debate revolves around the phenomenon of adult sea turtles travelling thousands of kilometres to return to the beach on which they were born, to lay another generation of eggs. How do they perform such pinpoint navigation?

While theories range from the elusive turtles using the earth's magnetic field, their sense of smell, ocean currents and landmarks to return to their birthplace, it is indisputable that none of this can be achieved without what biologists call 'imprinting': the sensory clues the birth beach impresses upon the sea turtles which enable them to find their way back and continue the cycle of life.

'Because of imprinting, it [artificial incubation] is not recommended at all,' says Frazer McGilvray, a marine biologist and co-author of a comprehensive report, written on behalf of Hong Kong Marine Conservation Society, on the local green turtles, the only sea turtle known to nest in Hong Kong. 'You won't find any kind of biologist who will argue with that.'

Yet the AFCD has incubated the eggs of green turtles three times in the past four years. This year's crop of Chelonia mydas was dug up two weeks after being discovered on June 25 during a routine patrol by game wardens who camp on the island during the summer breeding season.

What will these turtles remember? Will they recall hatching in a device resembling a microwave oven in a Shamshuipo laboratory, then being plopped into an aquarium for three weeks, all the while being handled by technicians in white gloves?

'Our first priority is to leave eggs in-situ for natural incubation,' responds Simon Chan Kin-fung, a senior wetland and fauna conservation officer who has overseen the green turtles for four years. 'However, two weeks of heavy rains shortly after the eggs laid had us worried that the [porous] eggs might suffocate because of their submergence in water.'

The risk of submergence is also a factor at another nesting site at Big Wave Bay, near Shek O, where eggs have been discovered laid too close to the water.

Hong Kong's green turtles are part of a larger subpopulation that also nests in Guangdong province. The practice of playing midwife is more common in southern China, where hatcheries rather than incubators are used to maximise survival rates.

At Gangkou National Nature Reserve in Huidong, 180 km northeast of Shenzhen, the baby turtles are experimentally raised for different periods, from a few months up to a year, says Chan, who has worked closely with the reserve since 1998. It's an attempt to thwart natural selection, and allow the turtles to grow in size, thus reducing their chances of becoming a sea snack.

Hong Kong's batch was released three weeks after being hatched because the AFCD waited until the baby turtles' yolk sacs, which hang from their bellies at birth like an umbilical cord, were absorbed. They are eventually consumed by a small hole in their stomachs, which then heals.

As Chan sees it, artificial incubation can ensure a higher hatch rate - 70 per cent for this summer's batch in Hong Kong. Researchers can then gather biological data and the hatchlings provide an educational opportunity for the public. 'I see no reason why headstarting some hatchlings should not be done,' Chan says.

Others argue such practice interferes with the fundamentals of nature. 'It's like playing God,' says McGilvray. 'Headstarting should only be done in unusual circumstances, like when flooding causes water tables to rise and puts the eggs at risk. It's a last, last resort.'

Either way, the effect of man's meddling is difficult to gauge for many reasons. Sea turtles are still, largely, a mystery of the deep and no one knows exactly when or how imprinting occurs. Extensive research data is also lacking, with official nesting numbers having been kept here for only the past four years. In 1998, 12 turtles nested at Sham Wan; in 1999, zero; in 2000, three; and this year, one. And though Gangkou's records go back nearly 20 years, they are characterised by erratic peaks and valleys and prove inconclusive, says Chan.

Michael Lau Wai-neng, a reptile expert and senior conservation officer with Kadoorie Farms, says anecdotal evidence strongly suggests a decrease in the local population. 'Fifty years ago turtle eggs were commonly sold in markets, so there had to have been a more substantial population.'

Reports in this newspaper show Lamma villagers harvested turtle eggs - traditionally regarded as a delicacy and an aphrodisiac - as recently as 1996. But this is no longer the case, says Chan, who has spearheaded an educational drive among the islanders, informing them of the olive-coloured animals' ecological value as well as the fact the eggs are no more nutritious than those of chickens. In 1999, Sham Wan was designated a restricted beach under the Wild Animals Protection Ordinance and is closed to the general public from June to October.

Biologists can only speculate on the size of the South China population. Further compounding the conundrum, the turtles have an irregular breeding cycle and grow very slowly: they can take up to 30 years to reach sexual maturity, with a life span of possibly more than 70 years.

AFCD theorises that the local green turtle population lives near Hainan Island or further south, near the Paracel Islands in the South China Sea; McGilvray believes they migrate from Mexico. Either way, the journey from feeding ground to birth beach is an epic undertaking after which the reptile spends hours dragging its 200-kilogram hulk across a beach to dig a 60cm-deep hole and lay more than 100 eggs. The task is so arduous the species lays eggs only every two to three years. They can lay several clutches of eggs in a nesting season.

'Determining a [population] trend requires long-term monitoring, so we can't make any predictions,' says Chan. It could be many more years before clues begin to surface, he says.

While other parts of the world have been tagging turtles for more than 30 years, AFCD only began a tagging programme last year and managed to place a metal clip, HK-001, on the flipper of one turtle.

But the best hope for learning more about these creatures lies with a hi-tech tracking programme begun this summer at Gangkou. In August, Chan helped biologists there glue satellite transmitters, costing $20,000 apiece, to the shells of three turtles. Experts hope to follow the turtles' progress through downloaded satellite data to get details of their feeding grounds, migration habits and how often they nest.

'The Hong Kong population can't be separated from that of southern China,' says Chan. 'If we're lucky, this project will help consolidate a plan for future conservation.' Southern China's remnant population is likely to depend on it.