POLICE believe mainlanders stole fish from a Hong Kong trawler off the Ninepins yesterday after damaging a net worth $3,000. It prompted police concern about a possible revival of theft at sea, rampant in Pak Sha Wan (Hebe Haven) a year ago. Police were told the owner of the Shau Kei Wan-based vessel had laid a net on a float six kilometres east of the Ninepins overnight. Several mainland sampans had been seen in the area, police said. 'It was later discovered a fishing net had been cut. 'We believe the suspected mainlanders might have damaged the net to get the catch quickly or to vent their anger if there were no fish inside,' he said. Two police launches arrived at the scene at noon to conduct a sweep but the boats had left.