For conservationists, sharks spark curiosity and concern. Hong Kong's surprisingly high kill rate - since 1991 all seven attacks by sharks on humans have proved fatal - spreads fear among swimmers. Conservationists are concerned about survival too - of the sharks. About 380 species of sharks exist worldwide, many of which migrate huge distances, but their lives are barely documented due to the difficulties of studying them. Unregulated fishing for their oil, fins, skin and meat may kill up to 70 million sharks a year, threatening the future of many species. The trade in fins - for sharks fin soup - represents perhaps sharks' greatest enemy with rising demand from Hong Kong, Taiwan, Singapore and China threatening populations around the world. Hong Kong, the world capital of sharks fin soup and the most important entrepot, imports up to six million kilograms from 125 countries each year. Harald Kvam of Maritime Mechanic Ltd has invested $10 million in a hi-tech vessel, equipped with sonar, which will allow the first insight into the habits of Hong Kong sharks. Migrating sharks may be lured into territorial waters by schools of fish or organic pollutants from the sewage spewed into the sea. Bite marks suggest tiger sharks are responsible for the fatal attacks but he believes great white sharks also cruise Hong Kong's waters. And Mr Kvam has his eyes firmly set on 'special ones' he plans to catch, tag with a sonar device and track. 'We have not seen very big ones - only three metres - these are not the ones we are looking for,' he said. Mr Kvam says his ground-breaking research can only plug a few gaps in the gaping knowledge about sharks in Hong Kong - but it will go a long way towards explaining the 'totally bizarre' series of fatalities. Until then, sharks may continue to wreak unwitting revenge on a territory whose voracious appetite for traditional soup threatens their species' existence.