Tracing the illicit Peruvian delicacy: proof-of-concept multiplex-PCR for the simultaneous detection of seven commercial Macrobrachium prawn species

The genus Macrobrachium (Decapoda, Palaemonidae) comprises nearly 300 prawn species distributed worldwide. At least nine of these species naturally inhabit the Pacific slope river systems of Peru, where most sustain significant artisanal fisheries and are highly prized as a luxury delicacy in the nations traditional cuisine. Here, we developed and validated a multiplex PCR assay with species-specific primers to identify seven Macrobrachium species of economic importance to Peru. Through robust validation, our assays achieved high specificity and efficiency, enabling fast and simultaneous identification of the seven target species. The utility of our novel multiplex PCR assay was evaluated as a proof-of-concept tool for conducting the first molecular monitoring of species diversity and illegal trade in Peruvian prawns across different commercial sectors. Among the 51 analyzed commercial prawn samples, a total of four species were detected, including M. caementarius (82.4%), M. rosenbergii (11.8%), M. americanum (3.9%), and M. gallus (1.9%). Notably, our molecular monitoring in restaurants revealed the first evidence of illegal trade in native wild-caught prawns in La Libertad region occurring during the reproductive closed season, when only the market of the exotic farmed prawn M. rosenbergii is permitted. These findings underscore the urgent need for enhanced monitoring programs in prawn fisheries in northern Peru, as current efforts are mainly focused on more productive central and southern regions. Our multiplex PCR assay provides a robust and efficient tool that can assist authorities and researchers in monitoring efforts, combating illegal trade, conducting diversity research, and supporting conservation.