Trophic ecology of the blue shark (Prionace glauca) based on stable isotopes (δ13C and δ15N) and stomach content

Hernández-Aguilar, Sandra Berenice; Escobar-Sánchez, Ofelia; Galván‐Magaña, Felipe; Abitía-Cárdenas, Leonardo Andrés

doi:10.1017/s0025315415001393

Cited by 31 publications

(30 citation statements)

References 36 publications

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“…Heterodontus francisci presented many empty stomachs (41.03%) compared to what has been reported for other Heterodontiformes species (Powter et al, ; Segura‐Zarzosa et al, ), but this was consistent with studies of other elasmobranch species (Alderete‐Macal, ; Escobar‐Sánchez, Abitia‐Cardenas, & Galván‐Magaña, ; Hernández‐Aguilar, Escobar‐Sánchez, Galván‐Magaña, & Abitia‐Cárdenas, ). This may be due to the fishing method or gear used to catch elasmobranchs, with gillnets set at sunset (when this sharks feed) and checked the following morning.…”

Section: Discussionsupporting

confidence: 88%

Feeding habits of the horn sharkHeterodontus francisci(Girard, 1855) in the northwest of Baja California Sur, Mexico

et al. 2020

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The feeding habits of the horn shark, Heterodontus francisci (Girard, 1855), were examined in the area of Bahía Tortugas, Baja California Sur, Mexico in the spring, summer and fall of 2014. A total of 78 stomachs were collected, of which 46 (59%) contained food and 32 (41%) were empty. According to the percent Index of Relative Importance (%IRI), the most important prey categories in H. francisci's diet were anomurans (66%), cephalopods (7.2%), lobsters (4.7%), fishes (4.2%) and sea urchins (2.3%). The main prey were the anomuran Blepharipoda occidentalis (65.2%), the octopus Octopus bimaculatus (5.4%), the lobster Panulirus interruptus (4.7%) and the sea urchin Echinometra vanbrunti (2.6%). According to the Levin standardized Index (Bi), the trophic niche breadth in H. francisci is low (Bi = 0.21), making it a specialist predator. The species was classified as a tertiary consumer (trophic position = 4.06).

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Section: Discussionsupporting

confidence: 88%

Feeding habits of the horn sharkHeterodontus francisci(Girard, 1855) in the northwest of Baja California Sur, Mexico

et al. 2020

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“…Moreover, the patterns of trophic position across size classes were different: consistently with isotopic niche patterns, isotopic values and TP SIA subtly increased across size classes, especially in mpun, also revealing the highest values in adult mmus, while TP SCA did not. Slight variations between the two methods have already been observed in 80 and 81 and have been linked to the intrinsic differences of the methodological approaches. www.nature.com/scientificreports/ Although the mean trophic position of both species was overall lower than previous results for maturing specimens of Mustelus spp.…”

Section: Discussionmentioning

confidence: 99%

Ontogenetic trophic segregation between two threatened smooth-hound sharks in the Central Mediterranean Sea

Lorenzo

Vizzini

Signa

et al. 2020

Sci Rep

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Elasmobranchs are among the species most threatened by overfishing and a large body of evidence reports their decline around the world. As they are large predators occupying the highest levels of marine food webs, their removal can alter the trophic web dynamic through predatory release effects and trophic cascade. Suitable management of threatened shark species requires a good understanding of their behaviour and feeding ecology. In this study we provide one of the first assessments of the trophic ecology of the "vulnerable" smooth-hounds Mustelus mustelus and M. punctulatus in the central Mediterranean Sea, based on stomach contents and stable isotope analyses. ontogenetic diet changes were addressed by comparing the feeding habits of three groups of individuals: juveniles, maturing and adults. our results highlighted that the two species share a similar diet based mostly on the consumption of benthic crustaceans (e.g. hermit crabs). their trophic level increases during ontogeny, with adults increasing their consumption of large-sized crustaceans (e.g. Calappa granulata, Palinurus elephas), cephalopods (e.g. Octopus vulgaris) and fish (e.g. Trachurus trachurus). our results provide also evidence of ontogenetic shifts in diet for both species showing a progressive reduction of interspecific trophic overlap during growth. The results of this study contribute to improve the current knowledge on the trophic ecology of these two threatened sharks in the Strait of Sicily, thus providing a better understanding of their role in the food web. Elasmobranch species are commonly recognized to be important predators in the marine realm 1 and play a crucial role in regulating marine ecosystems 2,3. Greater awareness of the trophic ecology of sharks can provide important information about the role they play during their life cycles and improve understanding of marine communities' structure and functioning. Many decades of severe human impacts have led to a rapid decline of many elasmobranch species around the world 4,5 , exacerbated by their biological vulnerability (e.g. slow growth rate, low fecundity, and late age at maturity) 2,5. As a consequence, many shark species are now registered by the IUCN as threatened or endangered 6. It has been shown that the decline of elasmobranch species has had marked ecological consequences 7,8. The loss of predators may negatively alter the food chain, triggering new interactions among species and marine ecosystem degradation 9. Therefore, improved knowledge about the elasmobranch trophic ecology, including the prey consumed, trophic level, ontogenetic diet changes, especially in the Mediterranean species, can play a crucial role in the development of new fishery management strategies. In fact, resource partitioning is one of the main processes for the coexistence of species 10. Partitioning, which has been observed in several organisms 12−14 , can occur along the space, time, or feeding niche axes 11 , during the same or at different

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“…These broad trophic niches of marine turtle are unlike those found in other marine predators. SIA of marine predators as varied as squid (Navarro et al, ), bony fishes (Torres‐Rojas et al, ; Pethybridge et al, ), sharks (Estrada et al, ; Hernandez‐Aguilar et al, ), and cetaceans (Abend & Smith, ; Hooker et al, ; Herman et al, ) consistently exhibit a narrow isotopic niche indicating feeding at a single, usually high, trophic level. What is even more remarkable is that this pattern of feeding across multiple trophic levels occurs in three species that otherwise exhibit trophic specialisations for certain types of prey – D. coricaea (gelativory), C. caretta (durophagy) and E. imbricata (spongivory).…”

Section: Discussionmentioning

confidence: 99%

Beyond trophic morphology: stable isotopes reveal ubiquitous versatility in marine turtle trophic ecology

2019

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The idea that interspecific variation in trophic morphology among closely related species effectively permits resource partitioning has driven research on ecological radiation since Darwin first described variation in beak morphology among Geospiza.Marine turtles comprise an ecological radiation in which interspecific differences in trophic morphology have similarly been implicated as a pathway to ecopartition the marine realm, in both extant and extinct species. Because marine turtles are charismatic flagship species of conservation concern, their trophic ecology has been studied intensively using stable isotope analyses to gain insights into habitat use and diet, principally to inform conservation management. This legion of studies provides an unparalleled opportunity to examine ecological partitioning across numerous hierarchical levels that heretofore has not been applied to any other ecological radiation. Our contribution aims to provide a quantitative analysis of interspecific variation and a comprehensive review of intraspecific variation in trophic ecology across different hierarchical levels marshalling insights about realised trophic ecology derived from stable isotopes.We reviewed 113 stable isotope studies, mostly involving single species, and conducted a meta-analysis of data from adults to elucidate differences in trophic ecology among species. Our study reveals a more intricate hierarchy of ecopartitioning by marine turtles than previously recognised based on trophic morphology and dietary analyses. We found strong statistical support for interspecific partitioning, as well as a continuum of intraspecific trophic sub-specialisation in most species across several hierarchical levels. This ubiquity of trophic specialisation across many hierarchical levels exposes a far more complex view of trophic ecology and resource-axis exploitation than suggested by species diversity alone. Not only do species segregate along many widely understood axes such as body size, macrohabitat, and trophic morphology but the general pattern revealed by isotopic studies is one of microhabitat segregation and variation in foraging behaviour within species, within populations, and among individuals.These findings are highly relevant to conservation management because they imply ecological non-exchangeability, which introduces a new dimension beyond that of genetic stocks which drives current conservation planning.Perhaps the most remarkable finding from our data synthesis is that four of six marine turtle species forage across several trophic levels. This pattern is unlike that seen in other large marine predators, which forage at a single trophic level according to stable isotopes. This finding affirms suggestions that marine turtles are robust sentinels of ocean health and likely stabilise marine food webs. This insight has broader significance for studies of marine food webs and trophic ecology of large marine predators.Beyond insights concerning marine turtle ecology and conservation, our findings also have broader impli...

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Trophic ecology of the blue shark (Prionace glauca) based on stable isotopes (δ¹³C and δ¹⁵N) and stomach content

Cited by 31 publications

References 36 publications

Feeding habits of the horn sharkHeterodontus francisci(Girard, 1855) in the northwest of Baja California Sur, Mexico

Feeding habits of the horn sharkHeterodontus francisci(Girard, 1855) in the northwest of Baja California Sur, Mexico

Ontogenetic trophic segregation between two threatened smooth-hound sharks in the Central Mediterranean Sea

Beyond trophic morphology: stable isotopes reveal ubiquitous versatility in marine turtle trophic ecology

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