More than five tonnes of coral groupers have been seized in Hong Kong from a cross-border ring who used speedboats to smuggle huge quantities of fish into mainland China.Eight people have been arrested for their alleged role in the syndicate, which sought to evade hefty mainland taxes, a Hong Kong customs official said on Thursday.The HK$1 million (US$128,000) haul, imported to the city by air from the Philippines and Indonesia and bound for the Yantian port of Shenzhen, was seized at a pier in…