Retrospective stable isotopes of vertebrae reveal sexual ontogenetic patterns and trophic ecology in oceanic whitetip shark, Carcharhinus longimanus

Abstract

There is a common phenomenon in nature whereby some animals have differences in their ontogenetic changes in dietary preferences between sexes, especially apex predators. These reflect changes in the needs of development during their lifetimes. Apex predators potentially have diverse dietary niches and a large impact on the trophic dynamics within ecosystems. However, the difference in life history between males and females often leads to increased difficulty in management and conservation. In this study, 25 oceanic whitetip sharks, Carcharhinus longimanus, were collected from the central and eastern tropical Pacific. Retrospective stable isotope analysis of vertebrae was used to evaluate the potential ontogenetic differences in feeding habits and niche width between sexes. Results showed that C. longimanus had a wide range of δ13C values (−18.1 to −12.3‰) and δ15N values (8.9–14.8‰). However, males and females had similar trophic positions with large niche overlap at similar growth stages. Both sexes had increasing δ13C values but relatively constant δ15N values along the vertebrae. These results indicated that male and female C. longimanus may share similar feeding strategies and movement patterns. The results presented in this study enhance our understanding of sexual ontogenetic patterns and ecological role of C. longimanus and highlighted the applicability of vertebrae for characterizing shark life‐history traits.

Isotopic life‐history signatures are retained in modern and ancient Atlantic bluefin tuna vertebrae

“…The results show δ 13 C, δ 15 N and δ 34 S isotope values can vary significantly throughout the growth axes of BFT vertebrae, probably reflecting the environments and prey foraged by fish over several years prior to capture. Clearly, like elasmobranch vertebrae (Carlisle et al, 2015;Shen et al, 2022), BFT vertebrae do not record a perfect isotopic chronology because juvenile bone collagen and muscle signatures (e.g., c. 16‰ δ 13 C, 5‰ δ 15 N) reflecting Mediterranean planktonic diets (Rumolo et al, 2020;Sarà & Sarà, 2007) were not measured in serial sections. Therefore, the authors propose, using their age 5 specimen, that a maximum of 4 years of life-history signatures may be retained, whereas early-life signatures are lost due to resorption during bone growth.…”

“…These are c . 1–2‰ variation in both δ 13 C and δ 15 N values over the life span of 10–15‐year‐old individuals, which studies generally agree represents a multi‐year signal instead of a perfect chronology (Carlisle et al ., 2015; Estrada et al ., 2006; Kerr et al ., 2006; Shen et al ., 2022). In teleosts, investigations are more recent and are as yet restricted to mostly anadromous Salmonidae spp., Pleuronectidae spp.…”

Inferring habitat use of the Pacific White Shark using vertebral chemistry

“…This raises the possibility that nursery areas may be distinguished based on the isotopic composition of a vertebrae's edge of neonates and young of the year who are still feeding in the nursery area. In contrast, the isotopic composition of the vertebral tissue laid down after the BM in oceanic habitat-dwelling sharks that undergo intrauterine placental feeding, such as the oceanic White Tip Shark (Carcharhinus longimanus) and the Blue Shark (Prionace glauca), appears to solely follow the maternal contribution and can thus be used to infer feeding region, rather than nursery areas of the young (Estupiñań-Montaño et al, 2019;Shen et al, 2021).…”

“…The d 13 C and d 15 N values of subsamples taken from the recently deposited vertebral edge of sharks reflects local foraging, and in the case of young sharks, the material laid down after the birth mark indicates a mixture of both maternal feeding from eggs within the womb and maternal supply (e.g. uterine milk, yolk sac placenta) in late-term embryos (Estupiñań-Montaño et al, 2019;Tomita et al, 2022), as well as foods consumed in their nursery habitats as neonates (Estrada et al, 2006;Shen et al, 2021). In older sharks, determination of isotopic values of vertebrae subsamples taken longitudinally along the axis of outward radial growth allows changes in feeding habits and foraging regions to be characterized throughout ontogeny (Estrada et al, 2006;Kim et al, 2012;Estupiñań-Montaño et al, 2019;Estupiñań-Montaño et al, 2021b).…”

Vertebral microchemistry as an indicator of habitat use of the oceanic whitetip shark Carcharhinus longimanus in the central and eastern Pacific Ocean

“…Given reabsorption is thought to be limited, trace elements are archived in annular bands and reflect the retrospective habitat and environmental conditions an individual experiences (Elsdon et al, 2008;Livernois et al, 2021;McMillan et al, 2017;Smith et al, 2016;Tillett et al, 2011). Complementary to trace elements, stable carbon and nitrogen isotope values (δ 13 C and δ 15 N) are proven intrinsic markers for elucidating habitat shifts in sharks (Carlisle et al, 2015;Kim et al, 2012;Madigan et al, 2015Madigan et al, , 2021Shen et al, 2022). The distinct isotopic composition of primary producers (and associated consumers) across oceanic subregions or even between coastal and estuarine environments as a result of localized oceanographic and biogeochemical regimes, can be used in conjunction with tissue sampling of predators to identify individual movements between systems (Madigan et al, 2021;Shipley et al, 2021).…”