A massive increase in fish bombing has sparked a crackdown by police and fisheries officials. The Agriculture and Fisheries Department is to call for a 20-fold rise in fines from $10,000 to $200,000 to deter fishermen from fish bombing. District Commander of Marine Outer Waters, David O'Brien, will reveal the extent of the problem at a marine conservation conference this weekend. He said fish bombing fell within the Marine Police remit of preventing crime and ensuring safety at sea. 'Marine Police officers, by the nature of their job, have an interest in the sea. We are all well aware of the destruction and damage to the ecological system that indiscriminate and reckless use of explosives causes.' Fish bombs - crude devices mainly consisting of a fistful of dynamite - are used by sampans plying the waters of the northeast New Territories around Double Haven and Kat O. Seizures of explosives have increased 2,000 per cent to nearly 370 kilograms in the last four years and police say that cheap dynamite, widely used along China's fast developing coast, is fuelling the illegal fishing practice. Possession of explosives carries a 14-year prison sentence but prosecuting the culprits is difficult because fishermen can throw the evidence overboard. If police find no explosives and only the dead fish aboard, fishermen can only be charged under the Fisheries Protection Ordinance, which carries a maximum fine of $10,000 and six months' imprisonment.