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Along the Pacific coast of Baja California Sur (PCBCS), the banded guitarfish (Zapteryx exasperata), shovelnose guitarfish (Pseudobatos productus) and bat ray (Myliobatis californica) are highly abundant. Their ecological roles as predators in demersal communities can be key in this ecosystem. To better understand their trophic relationship in the PCBCS, stable isotopes analysis of carbon (?¹³C) and nitrogen (?¹5N) were used. Muscle samples (n = 265) were collected from shovelnose guitarfish (n = 94), banded guitarfish (n = 87) and bat ray (n = 84). We observed high variability in stable isotopes values, ?¹³C and ?¹5N of shovelnose guitarfish ranged from -18.53 to -12.85‰ and 15.93‰ to 20.37‰, respectively; banded guitarfish from -18.12‰ to -13.57‰ and 14.41‰ to 19.26‰, respectively; and bat ray from -17.73‰ to -13.98‰ and 13.97‰ to 18.46, respectively. Statistically significant interspecific differences were found (p < 0.05) for ?¹³C and ?¹5N values, as bat ray showed a lower mean ?¹5N value and less negative mean ?¹³C value. Mature male (MM) bat ray) showed significantly higher ?¹5N values and shovelnose guitarfish (MM) significantly lower ?¹³C values compared to other cohorts. Isotopic niche analysis using Bayesian ellipses (SEAc) indicated shovelnose guitarfish occupies the widest isotopic niche compared with bat ray and banded guitarfish. Based on SEAc, the banded guitarfish overlapped 0.46 with the shovelnose guitarfish, while the bat ray overlapped 0.38 and 0.39 with banded and shovelnose guitarfish, respectively. Reported data suggest there is a relative overlap among all species, with probably greater amount of partitioning between the bat ray and the other two species.

Palabras clave: batoids; Carbon Nitrogen Stable Isotopes; Trophic ecology

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