title: Impact of the 2015 El Niño-Southern Oscillation on the Abundance and Foraging Habits of Guadalupe Fur Seals and California Sea Lions from the San Benito Archipelago, Mexico.
abstract: The abundance of California sea lions (Zalophus californianus) (CSLs) and Guadalupe fur seals (Arctocephalus philippii townsendi) (GFSs) from the San Benito Archipelago (SBA) was determined through nine monthly surveys in 2014-2015. Assessment of their foraging habits was examined based on the isotopic analysis of pups (maternal indicators) (SIAR/SIBER-R). Environmental variability between 2014 and 2015 was also analyzed, in terms of sea surface temperature (SST) and chlorophyll (Chl-a) concentration. Both otariids reached their highest abundance in July of both years; however, relative to 2014, the 2015 survey showed a 59.7% decline in the total GFS abundance and a 42.9% decrease of GFS pups, while total CSL abundance decreased 52.0% and CSL pup presence decreased in 61.7%. All monthly surveys for both otariids showed a similar trend (>50% decrease in 2015). Compared to 2014, the 2015 GFSs isotopic niche was three times larger (2.0 in 2015, 0.6 in 2014) and the δ13C was significantly lower. CSLs also showed significantly lower δ13C and higher δ15N in 2015. Interannual segregation was greater for CSLs, and their pup body mass was also significantly lower during the 2015 breeding season (mean = 8.7 kg) than in the same season of 2014 (mean = 9.9 kg). The decrease in δ13C for both otariids reflected a more oceanic foraging; most likely associated with the decline in primary productivity in surrounding areas to the SBA, related to a higher SST caused by the 2015 ENSO, with a subsequent increase in foraging effort. These would explain the fewer observed individuals on land, especially pups, which showed diminished body condition (CSLs). This study highlights the importance of marine mammals as sentinel species that respond dynamically to changes in environment, providing valuable information on the effect of ENSO on pinnipeds in Mexican waters.
authors.affiliation: Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional (CICIMAR-IPN), Departamento de Pesquerías y Biología Marina, Ave. IPN s/n Col. Playa Palo de Santa Rita, 23096, La Paz, Baja California Sur, Mexico.
authors.forename: Fernando R
authors.initials: FR
authors.lastname: Elorriaga-Verplancken
authors.affiliation: Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional (CICIMAR-IPN), Departamento de Pesquerías y Biología Marina, Ave. IPN s/n Col. Playa Palo de Santa Rita, 23096, La Paz, Baja California Sur, Mexico.
authors.forename: Gema E
authors.initials: GE
authors.lastname: Sierra-Rodríguez
authors.affiliation: Universidad Autónoma de Baja California Sur, Departamento Académico de Biología Marina, Carretera al sur, km 5.5, Apartado Postal 19-B, 23080, La Paz, Baja California Sur, México.
authors.forename: Hiram
authors.initials: H
authors.lastname: Rosales-Nanduca
authors.affiliation: Unidad de Microbiología Básica y Aplicada, Facultad de Ciencias Naturales, Universidad Autónoma de Querétaro, Av. de las Ciencias S/N, Juriquilla, 76230, Querétaro, Qro, México.|The Marine Mammal Center, 2000 Bunker Road, Sausalito, California, 94965, United States of America.
authors.forename: Karina
authors.initials: K
authors.lastname: Acevedo-Whitehouse
authors.affiliation: Universidad Autónoma de Baja California Sur, Departamento Académico de Biología Marina, Carretera al sur, km 5.5, Apartado Postal 19-B, 23080, La Paz, Baja California Sur, México.
authors.forename: Julieta
authors.initials: J
authors.lastname: Sandoval-Sierra
mesh_terms: D000818:Animals; D001947:Breeding; D002247:Carbon Isotopes; D059000:El Nino-Southern Oscillation; D004777:Environment; D005247:Feeding Behavior / Q000502:physiology*; D046069:Fur Seals / Q000502:physiology*; D005843:Geography; D062312:Islands; D007553:Isotope Labeling; D008800:Mexico; D009587:Nitrogen Isotopes; D046070:Sea Lions / Q000502:physiology*; D012621:Seasons; D013696:Temperature
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes