DNA analysis has been used by law enforcement officials for many years, usually to track down murderers or rapists. Now, it's being used to track down criminals of a different sort, says New Scientist's Nic Fleming: those that catch and sell fish illegally. Many key species of fish have been overfished in some locations while they thrive in others. Some governments have limited the numbers and types of fish that may be caught in certain areas, and now, genetic tests are available from a group called FishPopTrace to help authorities ascertain the origins of fish and fish products, Fleming says. The team, made up of researchers from 15 different institutions in Europe have sequenced thousands of samples of Atlantic cod, European hake, common sole, and Atlantic herring and have identified several hundred SNPs that their tests use to tell each variety of fish from another, and which body of water a particular fish comes from. The tests have been validated and running them costs around $10 a sample, Fleming adds. "The FishPopTrace team found that a test using 20 SNPs always correctly assigned Atlantic cod to one of the four major population groups. Using just one SNP, it got the origins of sole correct 96 per cent of the time, and with hake it was almost perfectly accurate with 10 SNPs," he says. An expert from the European Commission tells Fleming that he hopes the tests will not only be a powerful tool for enforcement, but will also act as a deterrent to illegal fishing.