Diet of the Burmeister's Porpoise ( Phocoena spinipinnis , Burmeister, 1865) on the Northern Coast of Argentina

Abstract

The Burmeister's porpoise ( Phocoena spinipinnis ) is a small cetacean endemic to South America, yet its diet is poorly known along Argentina's northern coast. We analyzed stomach ( n = 18) and intestinal ( n = 2) contents of 18 stranded or bycaught individuals collected from 1996 to 2024 between San Bernardo and Necochea (36°42′–38°33′S), Buenos Aires, Argentina. From the nine individuals with contents, 12 prey species were identified: 10 teleosts, 1 squid, and 1 crustacean. The striped weakfish ( Cynoscion guatucupa ) was the most important prey based on the index of relative importance (IRI% = 52.7), followed by Brazilian codling ( Urophycis brasiliensis ) (IRI% = 30.9). While the striped weakfish showed the highest frequency of occurrence (FO% = 27.8) and numerical abundance (NA% = 28.9), the Brazilian codling contributed most to biomass (BI% = 50.8). Teleost lengths ranged from 6.3 to 54.6 cm (23.7 ± 11 cm). All identified prey are of commercial interest, and 75% fall within commercial sizes. These results indicate a diet focused on demersal and pelagic coastal prey and suggest potential resource competition with local fisheries and sympatric predators. This is the first diet study for Burmeister's porpoise in northern Argentina and provides critical baseline data for its conservation.

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