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Martín Pestano, P., A., Trejo Ramírez, J.C., Hernández & F., Galván Magaña (2020). Trophic ecology through stomach contents and stable isotopes in the muscle of Mustelus henlei and Mustelus californicus in the area of Las Barrancas, Baja California Sur, México. Northeast Pacific Shark Symposium IV. La Pa, Baja California Sur, México, marzo 5 - 7, 2020, 1.

Trophic ecology through stomach contents and stable isotopes in the muscle of Mustelus henlei and Mustelus californicus in the area of Las Barrancas, Baja California Sur, México

Pablo Martín Pestano, Abel Trejo Ramírez, José Carlos Hernández y Felipe Galván Magaña

Mustelus henlei and Mustelus californicus are species very similar they share their distribution in the coasts of the peninsula of Baja California. They are important species in the Eastern Mexican Pacific fisheries but knowing if they are sharing niche trophic is unknown. In this study 61 stomachs of M. henlei and 26 stomachs of M. californicus were analyzed coming from the fishing camp Las Barrancas, B.C.S. The size range for M. henlei was between 61-86 cm of total length (TL) and for M. californicus 55-86 cm TL. Relative importance analysis (PSIRI) was used to determine the most important prey items. For M. henlei the most important prey item was Pleurocondes planiples 69%, and for M. californicus, crustacean remains 33.64% were the most abundant, followed by UOM (Unidentified Organic Matter) with 30.09%. Trophic amplitude presented a <0.6 value, indicating specialist habits to both species. Significative differences (p<0.05) were found between the stomach content of both species, displaying there is feeding segregation. On another hand, 44 muscle samples (22 to each species) were analyzed to stable isotopes. d15N and d13C mean values were of 17.08 ‰ ± 0.69 d15N y -17.76 ‰ ± 0.87 d13C to M. henlei and for M. californicus were 18.09 ‰ ± 0.52 d15N and -16.35 ‰ ± 0.36 d13C. Significant differences (p<0.05) were obtained between d15N and d13C isotopic values for both species. Isotopic niche analysis (SIBER) showed not exist a trophic overlap between these sharks. Both species displayed specialist habits (Variance = 0.47 M. henlei and 0.26 M. californicus). Concerning to trophic position, M. henlei presented a value of 3.9 opposite 4.2 of M. californicus, being tertiary carnivorous predators. With both techniques, results were very similar, despite these sharks are from the same genus and they were captured at the same spot, they present different trophic niches, which shows that to make a fishery management plan it is necessary to conduct studies by species and not consider them in the same trophic niche automatically because they belong to the same genus.

Palabras clave: Mustelus californicus; Mustelus henlei; Trophic ecology

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