In 2003, a geneticist used DNA markers called microsatellites to show that a fishing vessel had violated its quota by catching too many cod from the North Sea. It was a rare victory against the massive problem of illegal fishing. For technical reasons, however, microsatellite tests for identifying the local origins of caught fish haven't been widely adopted.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/fight-illegal-fishing-forensic-dna-gets-local
[2] http://admin.indiaenvironmentportal.org.in/category/author/erik-stokstad
[3] http://admin.indiaenvironmentportal.org.in/category/journal/science
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/marine-fisheries
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/europe
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/denmark