ARRESTS for drug trafficking more than tripled in the first quarter of this year over the same period last year, the latest crime figures show. Sixty-one people were detained between January and March last year, compared to 186 this year. But far from being alarming, the Commissioner for Narcotics, Mr Alasdair Sinclair, said the figures suggested that the police were becoming more effective in cracking down on drug offenders. He pointed out that if they included traffickers detained while in transit at Kai Tak, the statistics might not be a true indication of the demand for drugs in the territory. However, the Central Registry of Drug Abuse recorded an increase in new addicts last year, he said. The number of new drug abusers reported to the registry climbed about eight per cent, to 2,904 from 2,697 in 1991.