Discrimination of stable isotopes in fin whale tissues and application to diet assessment in cetaceans

Borrell, Asunción; Abad-Oliva, N.; Gómez–Campos, Encarna; Giménez, Joan; Aguilar, Àlex

doi:10.1002/rcm.6267

Cited by 117 publications

(172 citation statements)

References 48 publications

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“…3). Our finding is consistent with a more stenophagous diet of Mediterranean whales, which likely focus mostly on krill (Borrell et al, 2012). Tissues that integrate over weeks, such as skin, are much more likely to discriminate generalist diets than discrete samples from tissues which integrate variation over much longer time-scales, such as baleen plates (Bearhop et al, 2004).…”

Section: Isotopic Niche Analysissupporting

confidence: 87%

“…Half-life turnover rates were estimated to be 24.16 ± 8.19 days for carbon and 47.63 ± 19 days for nitrogen in skin of bottlenose dolphins (Gim enez et al, 2016). A krill-skin isotope enrichment was previously calculated for fin whales (D 15 N ¼ 2.8‰) (Borrell et al, 2012). We observed a wide distribution of d…”

Section: Intra-population Variationsmentioning

confidence: 52%

“…Nitrogen stable isotopes are therefore mostly used to estimate an animal's trophic level (Post, 2002). The abovementioned enrichment factors have been measured for several marine mammal species (Caut et al, 2011;Gim enez et al, 2016;Hobson et al, 1996) including fin whales (Borrell et al, 2012 15 N values in muscle and skin of 65 fin whales from the Mediterranean Sea and calculated the difference with data published previously for krill (Bentaleb et al, 2011). Since the first conceptualization of the ecological niche as an ndimensional hypervolume of which each dimension represent an environmental and/or resource requirement (Hutchinson, 1957), use of this concept has expanded in the ecological literature.…”

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confidence: 99%

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Isotopic niches of fin whales from the Mediterranean Sea and the Celtic Sea (North Atlantic)

Das

Holleville

Ryan

et al. 2017

Marine Environmental Research

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a b s t r a c tThe fin whale (Balaenoptera physalus) is the most abundant and widespread mysticete species in the Mediterranean Sea, found mostly in deep, offshore waters of the western and central portion of the region. In the Mediterranean, this species is known to feed mainly on krill, in contrast to its Atlantic counterpart, which displays a more diversified diet. The International Whaling Commission recognizes several managements units in the Atlantic and the Mediterranean Sea and the connectivity between these populations is still being debated. Questions remain about inter-individual feeding strategies and trophic ecology.The goal of this study was to compare isotopic niches of fin whales from the Mediterranean Sea and the Celtic Sea (North Atlantic). One could indeed expect that species displaying narrow niches would be more susceptible to ecosystem fragmentation and other anthropogenic impacts.

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Section: Isotopic Niche Analysissupporting

confidence: 87%

Section: Intra-population Variationsmentioning

confidence: 52%

mentioning

confidence: 99%

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Isotopic niches of fin whales from the Mediterranean Sea and the Celtic Sea (North Atlantic)

Das

Holleville

Ryan

et al. 2017

Marine Environmental Research

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“…To examine dietary niche position of predator groups in relation to capelin stable isotopic ratios, a best-fitting trophic discrimination factor was chosen for each group based on taxonomy and previous knowledge of diet. Values of 1.86‰ for δ 15 N and 0.46‰ δ 13 C for rockhopper penguins were applied to shearwater samples (Cherel et al, 2005), 3.1‰ for δ 15 N and −0.30‰ δ 13 C for ring-billed gull chicks (Hobson and Clark, 1992) were applied to gull chick samples, and 2.82‰ for δ 15 N and 1.28‰ δ 13 C for fin whales (Borrell et al, 2012) were applied to humpback whale samples.…”

Section: Discussionmentioning

confidence: 99%

Dietary Niche Shifts of Multiple Marine Predators under Varying Prey Availability on the Northeast Newfoundland Coast

et al. 2017

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Understanding species interactions among top marine predators and interactions with their prey can provide important insight into community-level responses to changing prey availability and the role of apex predators as indicators of ecosystem change. On the northeast Newfoundland coast, marine predators rely on capelin (Mallotus villosus), a dominant forage fish, as a food source. Capelin migrate into coastal regions to spawn during July, essentially transforming the food supply from low during early summer (i.e., pre-spawning) to high later in the summer (i.e., spawning). During July-August, 2016, we used stable isotopic ratios of nitrogen (δ 15 N) and carbon (δ 13 C) to investigate shifts in dietary niche metrics at the predator group-level (trophic position, dietary niche breadth) and community-level (niche overlap, trophic diversity) for multiple marine predators under varying capelin availability. Predator groups included non-breeding shearwaters (great shearwater Ardenna gravis, sooty shearwater A. grisea), humpback whales (Megaptera novaeangliae), and gull chicks (herring gull Larus argentatus, great black-backed gull Larus marinus). We also tested the sensitivity of community-level dietary metrics to a variety of published trophic discrimination factors. Tissue samples from shearwaters (blood cellular component), gull chicks (whole blood), and whales (skin), representing average diets over 2-3 weeks, were collected during three periods (early, mid, late) corresponding to increasing capelin availability. Isotopic niche breadth (Standard Ellipse Area, SEA b ) narrowed and trophic position shifted toward higher δ 15 N for all predator groups as capelin availability increased, suggesting a higher reliance on capelin. Trophic diversity (distance to centroid) decreased with increased capelin availability, while pairwise niche overlap between predator groups was highly variable and sensitive to trophic discrimination factors. Findings suggest that although capelin is the dominant forage fish during the summer, predators rely on capelin as prey to varying degrees. Combining species-and community-level metrics of dietary niche and trophic diversity may provide a more complete picture of predator responses to prey availability and, thus, may be important monitoring tools to indicate changes in the food supply of marine predators.

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“…In order to more accurately evaluate stable isotope data, tissue-specific diet-tissue discrimination values need to be determined for cetacean skin, as that is the tissue most easily obtained. There are currently only two published studies on cetacean diet-tissue discrimination values for skin (Caut et al, 2011;Borrell et al, 2012) but neither study was undertaken under controlled conditions or for an extended period of time.…”

Section: Introductionmentioning

confidence: 99%

Isotope turnover rates and diet-tissue discrimination in skin ofex situBottlenose Dolphins (Tursiops truncatus)

Browning

Dold

I-Fan³

et al. 2013

Journal of Experimental Biology

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Diet-tissue discrimination factors (Δ 15 N or Δ 13 C) and turnover times are thought to be influenced by a wide range of variables including metabolic rate, age, dietary quality, tissue sampled and the taxon being investigated. In the present study, skin samples were collected from ex situ dolphins that had consumed diets of known isotopic composition for a minimum of 8 weeks. Adult dolphins consuming a diet of low fat (5-6%) and high δ 15 N value had significantly lower Δ C ranged from 11 to 23 days with a significant difference between low fat (13.9±4.8 days) and high fat diets (22.0±0.5 days). Overall, our results indicate that while assuming a Δ 13 C value of 1‰ may be appropriate for cetaceans, Δ15 N values may be closer to 1.5‰ rather than the commonly assumed 3‰. Our data also suggest that understanding seasonal variability in prey composition is another significant consideration when applying discrimination factors or turnover times to field studies focused on feeding habits. Isotope retention times of only a few weeks suggest that, in addition, these isotope data could play an important role in interpreting recent fine-scale habitat utilization and residency patterns.

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Discrimination of stable isotopes in fin whale tissues and application to diet assessment in cetaceans

Cited by 117 publications

References 48 publications

Isotopic niches of fin whales from the Mediterranean Sea and the Celtic Sea (North Atlantic)

Isotopic niches of fin whales from the Mediterranean Sea and the Celtic Sea (North Atlantic)

Dietary Niche Shifts of Multiple Marine Predators under Varying Prey Availability on the Northeast Newfoundland Coast

Isotope turnover rates and diet-tissue discrimination in skin ofex situBottlenose Dolphins (Tursiops truncatus)

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