California sea lion population decline at the southern limit of its distribution during warm regimes in the Pacific Ocean

Pelayo‐González, Lili; González‐Rodríguez, Eduardo; Ramos-Rodríguez, Alejandro; Hernández‐Camacho, Claudia J.

doi:10.1016/j.rsma.2021.102040

Cited by 3 publications

(5 citation statements)

References 39 publications

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“…However, some of their prey are targeted by local artisanal and industrial fisheries, which explains by-catch of White Sharks by local fisheries inside the GC (Galvań-Magaña et al, 2010;Madigan et al, 2021;Malpica-Cruz et al, 2021). Further, thirteen California sea lion (Zalophus californianus) colonies are found in the GC mainly in the central and northern reaches which might serve as an important food source for adult White Sharks (Masper et al, 2019;Pelayo-Gonzaĺez et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Inferring habitat use of the Pacific White Shark using vertebral chemistry

et al. 2023

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The conservation and management of highly migratory sharks relies on understanding age-related movements and nursery habitat utilization. We reconstructed the habitat use and migratory history of young White Sharks (Carcharodon carcharias), a highly protected species, by utilizing natural chemical tracers (element:Ca ratios and stable isotope analysis, SIA) in vertebral cartilage growth bands. Two nursery areas in the northeastern Pacific are known, but migration patterns of immature White Sharks within the Gulf of California (GC) and natal philopatry are poorly understood. Vertebrae from coastal Mexican artisanal fisheries off central Baja California in the Pacific (12 neonates and juveniles; 139-280 cm total length) and the GC (3 subadults; 289-355 cm TL) were analyzed to characterize (1) trophic histories from collagen δ13C and δ15N values, and (2) in utero patterns and post-birth environmental histories from element:Ca time-series. Mean δ15N values from vertebral edges of GC sharks, representing the most recent feeding, was +5‰ higher than in the Pacific, reflecting the intense denitrification that permeates the regional food web and supporting SIA as tracers of migration between regions. A subadult from the GC likely resided within the system throughout its life, and two subadults migrated into the GC. Most neonate and juvenile sharks caught in the Pacific had SIA that did not overlap with those of the GC, but a single subadult likely migrated to the GC. Element:Ca ratios displayed ontogenetic trends, with Li:Ca, Zn:Ca, and Ba:Ca significantly higher before the birth mark in sharks captured in the GC. Edge values were significantly higher in Zn:Ca and Ba:Ca in the GC compared to the Pacific, suggesting elemental ratios may serve as tracers of migration between regions. Subadult sharks collected from GC displayed elevated maternal Zn:Ca and Ba:Ca, suggesting mothers may have resided in the GC for an extensive period pre-birth. Some White Sharks may reside within the GC from birth until at least the subadult stage (ca. 3 m TL), and there may be an unidentified nursery. Chemical tracers, coupled with genomic and tagging studies, should improve understanding of the importance of the GC to White Shark populations in the northeast Pacific.

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Section: Discussionmentioning

confidence: 99%

Inferring habitat use of the Pacific White Shark using vertebral chemistry

et al. 2023

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“…The striped marlin population may be critically important for linking this resource to other predators, such as sea birds, other teleost species, potentially rorqual whales, and in this study case, sea lions. Sea lion rookeries off the Baja California Peninsula are declining owing to oceanographic warm anomalies in recent years, which poses a potential negative impact on their trophic ecology [52,75,76]. Thus, the results of this study provide important background information on the trophic ecology of sea lions from this region.…”

Section: Discussionmentioning

confidence: 99%

California sea lions interfere with striped marlin hunting behaviour in multi-species predator aggregations

Hansen

Kurvers

Licht

et al. 2023

Phil. Trans. R. Soc. B

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The open ocean offers a suite of ecological conditions promoting the occurrence of multi-species predator aggregations. These mixed predator aggregations typically hunt large groups of relatively small and highly cohesive prey. However, the mechanisms and functions of these mixed predator aggregations are largely unknown. Even basic knowledge of whether the predator species' interactions are mutualistic, commensal or parasitic is typically missing. Moreover, recordings of attack and capture rates of marine multi-species predator aggregations, which are critical in understanding how and why these interactions have evolved, are almost completely non-existent owing to logistical challenges. Using underwater video, we quantified the attack and capture rates of two high-trophic level marine predators, California sea lions ( Zalophus californianus ) and striped marlin ( Kajikia audax ) attacking schools of fishes in the Southern California Current System, offshore the Baja California Peninsula. Recording over 5000 individual attacks across 13 fish schools, which varied in species, size and predator composition, we found that sea lions kleptoparasitized striped marlin hunts and reduced the frequency of marlin attacks and captures via interference competition. We discuss our results in the context of the phenotypic differences between the predator species and implications for a better understanding of multi-species predator aggregations. This article is part of the theme issue ‘Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes’.

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“…Differences in life history traits and environmental conditions exist between California sea lions from the Pacific coast of the Baja California peninsula and those from the Gulf of California off of the coast of mainland Mexico (Szteren and Aurioles-Gamboa 2011; López-Arvide 2014; Rosas-Hernández et al 2018; Pelayo-González et al 2021a, 2021b; Hernández-Camacho et al 2021), and geographic isolation between populations may be accelerating their genetic divergence (González-Suárez et al 2009). Previous genetic studies indicated that California sea lions are separated into 5 subpopulations (Fig.…”

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confidence: 99%

“…Currently, about 14% (53,000 individuals) of the species occurs on the Pacific coast of the Baja California peninsula, and only 6% (20,000 individuals) are in the Gulf of California—the remainder occur along the Pacific coast of the United States and Canada. The broader, positive trend in total population size could mask the 1 to 4% annual reduction of Gulf of California colonies (Pelayo-González et al 2021a, 2021b)—a trend that toward the risk of colonies disappearing in the coming decades, especially considering that expected loss of genetic variation in geographic isolated and smaller colonies could add to their risk of extinction (Schramm et al 2009; Rayas-Estrada and Hernández-Camacho 2019).…”

mentioning

confidence: 99%

“…Analyses show that most colonies within these subpopulations are experiencing declines in population size, with only a few colonies that are stable and 1 increasing (Elorriaga-Verplancken et al 2015; Hernández-Camacho et al 2021). Recent studies show that birth rates and population totals may be linked to a decrease in prey abundance (Adame et al 2020; Pelayo-González et al 2021a, 2021b).…”

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confidence: 99%

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Skull shape and size changes in different subpopulations of the California Sea Lion (Zalophus californianus) in Mexico

Aguilar Medrano,

Cruz Escalona,

Payán Alcacio

et al. 2023

Journal of Mammalogy

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California sea lions (Zalophus californianus) are distributed along the Gulf of California and northeastern Pacific coast. Genetic studies have suggested the existence of 3 to 4 subpopulations in Mexico—1 on the Pacific coast of the Baja California peninsula (PC) and 3 in the Gulf of California—but the extent of this divergence is unclear, and it remains unknown if these subpopulations are morphologically distinct. In this context, we analyzed variation in skull size and shape of adult males between 5 and 13 years of age among 2 (north and central) of the 3 subpopulations of Z. californianus from the Gulf of California and the PC in Mexico. However, since the sample sizes for the 2 subpopulations in the Gulf of California were small, we merged all samples into 1 that we called the Gulf of California (GC) subpopulation. Artificial neural networks and geometric morphometrics were used to analyze skull images to quantify the extent to which these geographically separated subpopulations are undergoing morphological divergence. Our results find no significant differences in size in any view between the 2 subpopulations, but significant differences in the morphology of the dorsal, ventral, and lateral views of the skull between the 2 subpopulations. Overall, Z. californianus from the GC subpopulation have wider and lower skulls, extended back and outward with a more voluminous (bulky) nuchal crest, and narrow rostrum in comparison with skulls of Z. californianus from the PC subpopulation. Results concur with a previous genetic-based study, demonstrating that Z. californianus from both subpopulations in Mexico are diverging in their skull morphology and perhaps suggesting that they are experiencing different evolutionary pressures.

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California sea lion population decline at the southern limit of its distribution during warm regimes in the Pacific Ocean

Cited by 3 publications

References 39 publications

Inferring habitat use of the Pacific White Shark using vertebral chemistry

Inferring habitat use of the Pacific White Shark using vertebral chemistry

California sea lions interfere with striped marlin hunting behaviour in multi-species predator aggregations

Skull shape and size changes in different subpopulations of the California Sea Lion (Zalophus californianus) in Mexico

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