Smugglers have tripled their prices for spiriting mainlanders into Hong Kong because they fear new marine boundaries make the trade more dangerous.
Among post-handover boundary changes, an agreement with Guangdong means mainland authorities now patrol half of Deep Bay.
Before July 1, the Hong Kong Government was responsible for the entire body of water.
Marine West Divisional Commander Acting Superintendent Jackie Ling Wai-po said: 'Mainland authorities now dispatch boats to patrol the northern part of Deep Bay every day, forming the first surveillance line in the area.
'The Hong Kong police patrol forms the second surveillance line. The doubled efforts make anti-illegal immigration and smuggling activities more effective.' The cost for illegal immigrants to take a wooden motorboat to Hong Kong has risen from a low of 300 yuan (HK$279) before the handover to more than 1,000 yuan now.
The total number of illegal immigrants arrested fell from 2,347 in 1995 to 1,666 in 1996 and just 1,046 last year.
