Mejía-Guarnizo, B.N., A., Ornelas-Vargas, F.J., García-Rodríguez, F.R., Elorriaga-Verplancken, F., Valenzuela-Quiñonez, T., Zenteno-Savín, D.A., Murillo-Cisneros & C.J., Hernández-Camacho (2025). Temporal dietary shifts in California sea lions at Los Islotes colony, Gulf of California. Regional Studies in Marine Science. 90: 104479. DOI: 10.1016/j.rsma.2025.104479.
Brenda N. Mejía-Guarnizo, Arelly Ornelas-Vargas 1, Francisco J. García-Rodríguez 1, Fernando R. Elorriaga-Verplancken 1, Fausto Valenzuela-Quiñonez, Tania Zenteno-Savín, Daniela A. Murillo-Cisneros y Claudia J. Hernández-Camacho 1
Studying the diet of the California sea lion (Zalophus californianus, CSL) provides information about its role as a biological indicator of ecosystem stability. The CSL breeding colony of Los Islotes, Gulf of California, is the only one in Mexico to increase its abundance in decades. However, beginning in 2015, colony size stabilized for a few years, resuming growth in 2020. These changes may be associated with variations in prey availability influenced by sea surface temperature (SST) anomalies in the area. CSL diet in this colony was evaluated from fecal samples and related to SST anomalies in the area. We identified more than 1400 fish otoliths from 229 samples obtained between 2015 and 2022. Prey importance (IIMP% index) and ecological and trophic indices were calculated. Diet structure was compared over time through multivariate analysis. From the SST anomalies, the climatic regimes in recent years were calculated. We assessed how these anomalies are associated with calculated indices through cross-correlations. Fish (n = 79) and cephalopod (n = 3) species were identified, including new species of commercial interest in the area. Few prey items had an importance index higher than 5 %; thus, we classified CSL from Los Islotes as plastic specialist. Individual specialization in diet was also observed. Dietary variation was not seasonal but annual, and cross-correlations showed a significant relationship between SST anomalies and ecological–trophic indices. A change in the composition and structure of the diet for CSL in Los Islotes has been observed since 2015 compared to previous decades.
Palabras clave: feeding habits; Hard remains; Prey; Trophic indexes; Individual specialization
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