Assessing illegal fishing and trade of Atlantic billfish and swordfish by DNA-based identification

Due to the morphological similarity between some billfish species, the International Commission for the Conservation of Atlantic Tunas (ICCAT) recommends the use of molecular tools to identify billfish at the species level to properly manage this imperiled group. In this study, species-specific swordfish and billfish identification was carried out by using PCR-RFLP and multiplex PCR of the mitochondrial COI gene. Samples were obtained during landings of the tuna fleet at the Public Fisheries Port of Santos (PFPS) and in the General Warehouse Company of Sao Paulo (CEAGESP), Brazil. A total of 87 samples from PFPS were identified: Kajikia albida, Tetrapturus georgii, T. pfluegeri, Makaira nigricans, and Istiophorus platypterus. At CEAGESP, 432 individuals were collected, and three species were detected: Xiphias gladius, I. platypterus and T. georgii. Some samples presented an unknown band pattern for PCR-RFLP, which were sequenced and identified as X. gladius. These findings demonstrate that billfishes protected by law are being caught by industrial fisheries, but they are not traded at the CEAGESP. We advocate continuous onboard and of landings fishing monitoring using molecular identification tools in accordance with ICCAT recommendations. We provided evidence that DNA-based methods are efficient in overcoming billfish misidentification in the Atlantic Ocean.