Using simple molecular markers for the identification of billfish traded in the Eastern Tropical Pacific

Billfishes (Xiphiidae and Istiophoridae) are economically important species. Unfortunately, these fish are part of the bycatch in many fisheries and are subject to unregulated trade. Another problem is inadequate identification, as diagnostic features are often removed when they are captured. This research aimed to design protocols based on PCR-RFLPs and PCR-Multiplex to carry out a relatively rapid and robust identification of billfish species of commercial interest in the Eastern Tropical Pacific. In silico PCR-RFLP analysis allowed the selection of six restriction enzymes; the enzyme HinfI was the most effective for species discrimination, while PvuII was the least effective. For the PCR-Multiplex, it was observed that the primers designed in silico amplify approximate sizes for their respective species and allow the identification of the species through the difference in band sizes in the agarose gels. These tools were tested on tissues from commercial sources, where it was possible to identify three species of billfishes (Kajikia audax, Makaira nigricans, and Xiphias gladius) and two species from other groups (Nematistius pectoralis and Thunnus albacares). The application of the protocols was successful in fresh tissue and processed (smoked) tissue. These protocols, implemented together, allow for greater support in the genetic identification of billfishes.