Intraspecific variability in diet and implied foraging ranges of whale sharks at Ningaloo Reef, Western Australia, from signature fatty acid analysis

Marcus, Lara; Virtue, Patti; Meekan, Mark G.; Thums, Michele; Nichols, Peter D.

doi:10.3354/meps11807

Cited by 23 publications

(47 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar intra‐population specialization in R. typus has also been suggested by differences in muscle δ 15 N in the Red Sea (δ 15 N range 5.8‰ to 10.5‰, n = 20; A. S. J. Wyatt and B. Kuerten, unpublished data ) and fatty acid compositions at Ningaloo Reef, Western Australia (Marcus et al. ), but in both cases, the influence of growth and baseline variation could not be determined. Such differences may reflect the relative amounts of individual feeding on benthic and deep‐water prey, with deep‐water foraging perhaps especially important during long‐distance migrations between aggregation sites (Rohner et al.…”

Section: Discussionsupporting

confidence: 58%

“…, Marcus et al. ). Continuing to unravel the relative importance of long‐distance migrations, deep ocean and shallow coastal productivity in supporting R. typus will greatly enhance our capacity to understand the response of the species to local and global perturbation.…”

Section: Discussionmentioning

confidence: 99%

“…, Marcus et al. ), while open ocean movements suggest utilization of prey concentrated by fronts (Ryan et al. ).…”

Section: Introductionmentioning

confidence: 99%

“…Evidence from fatty acid profiles also suggests intra‐population variation in feeding habits may exist in R. typus , independent of size and sex (Marcus et al. ).…”

Section: Introductionmentioning

confidence: 99%

“…The diet of R. typus outside of coastal aggregations is generally unknown. Fatty acid analyses have suggested that they may depend on deep-water zooplankton and fishes during long-distance migrations (Rohner et al 2013, Marcus et al 2016, while open ocean movements suggest utilization of prey concentrated by fronts (Ryan et al 2017). Careful isotopic analyses of R. typus may thus be particularly informative for understanding and comparing diets in and outside aggregations, especially given the species' threatened status and oceanic migrations which make lethal sampling and sustained feeding observations undesirable and difficult, respectively.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Enhancing insights into foraging specialization in the world's largest fish using a multi‐tissue, multi‐isotope approach

Wyatt

Matsumoto

Chikaraishi

et al. 2019

Ecological Monographs

View full text Add to dashboard Cite

Intra‐species variability in foraging strategies may be common, which has significant implications for efforts to understand and manage enigmatic species like the whale shark Rhincodon typus. The ecological relevance of differences in tissue isotopes within and between individuals in the context of foraging however depends on understanding tissue turnover times and carbon (Δ13C) and nitrogen (Δ15N) discrimination, which can vary with physiology, metabolism, and diet quality. Here, we examine isotope dynamics in captive R. typus as a basis for enhanced ecological insights into wild populations of the world's largest fish and other enigmatic species. A variable diet, principally consisting of two krill (Euphausia pacifica and Euphausia superba) provided an average of 48 ± 20 MJ/d (mean ± SD), or 2.7 ± 1.3 times basal metabolic requirements. On this diet, in agreement with allometric relationships, large body sizes (3,000–4,000 kg) were matched by slow plasma and cartilage turnover rates (empirically derived as 9 months and 3 yr, respectively), which provide tissue‐specific limits on the timescales over which we can isotopically detect diet changes in this species. Average diet‐to‐tissue discrimination showed significant variation between tissues (plasma and cartilage), and among growing and fasting individuals (Δ13C range, 1.5 to 5.5‰; Δ15N range, −0.1 to 2.9‰). Assimilation rates increased with temperature and were higher for the smaller E. pacifica (15 ± 2 mm) than E. superba (48 ± 2 mm). Growth significantly lowered both Δ15Nplasma and Δ15Ncartilage, with inappetence markedly reducing Δ15Nplasma and Δ13Cplasma, as well as significantly altering blood biochemistry. Captive findings facilitated the first robust multi‐tissue growth‐ and nutrition‐corrected isotope analysis of a wild R. typus population, suggesting individual foraging specialization on low trophic level mid‐ocean or coastal prey. Long‐term fasting during ocean‐basin‐scale migrations may be common and such metabolic effects should be carefully quantified when isotopically assessing intra‐species foraging differences. The metabolically constrained multi‐tissue, multi‐isotope approach described can facilitate ecological insights that are indispensable for effective conservation and management of globally threatened, but poorly understood, species by identifying differences in key foraging areas and target prey within and between individuals.

show abstract

Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

“…, Marcus et al. ), while open ocean movements suggest utilization of prey concentrated by fronts (Ryan et al. ).…”

Section: Introductionmentioning

confidence: 99%

“…Evidence from fatty acid profiles also suggests intra‐population variation in feeding habits may exist in R. typus , independent of size and sex (Marcus et al. ).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Enhancing insights into foraging specialization in the world's largest fish using a multi‐tissue, multi‐isotope approach

Wyatt

Matsumoto

Chikaraishi

et al. 2019

Ecological Monographs

View full text Add to dashboard Cite

show abstract

Regional movements of satellite‐tagged whale sharks Rhincodon typus in the Gulf of Aden

Andrzejaczek

Vely²,

Jouannet³

et al. 2021

Ecology and Evolution

View full text Add to dashboard Cite

Marine megafauna are typically highly mobile species with migration pathways that can cross the boundaries of multiple national jurisdictions (Block et al., 2011;Sequeira et al., 2018). These international movements may expose migrating animals to a number of anthropogenic threats, including fluctuating levels of fishing pressure and shipping activity, that together with the varying extent of legal protection encountered through movements and the conservative life histories of many megafauna species, can have large-scale impacts on populations (Hays et al., 2019). In addition, such movements complicate conservation and management efforts through the need for coordinated efforts among many nations and international organizations (Lascelles et al., 2014). A crucial first step in identifying the threats faced by marine megafauna and in mitigating their potential impacts on populations is to describe the distribution and movement patterns of these vulnerable species (Hammerschlag et al., 2011;Hays et al., 2016).Whale sharks (Rhincodon typus) are large (max. TL 20 m) elasmobranchs that live in warm temperate-tropical waters (Rowat &

show abstract

Detect and exploit hidden structure in fatty acid signature data

2017

View full text Add to dashboard Cite

Citation: Bromaghin, J. F., S. M. Budge, and G. W. Thiemann. 2017. Detect and exploit hidden structure in fatty acid signature data. Ecosphere 8(7):e01896. 10. 1002/ecs2.1896 Abstract. Estimates of predator diet composition are essential to our understanding of their ecology.Although several methods of estimating diet are practiced, methods based on biomarkers have become increasingly common. Quantitative fatty acid signature analysis (QFASA) is a popular method that continues to be refined and extended. Quantitative fatty acid signature analysis is based on differences in the signatures of prey types, often species, which are recognized and designated by investigators. Similarly, predator signatures may be structured by known factors such as sex or age class, and the season or region of sample collection. The recognized structure in signature data inherently influences QFASA results in important and typically beneficial ways. However, predator and prey signatures may contain additional, hidden structure that investigators either choose not to incorporate into an analysis or of which they are unaware, being caused by unknown ecological mechanisms. Hidden structure also influences QFASA results, most often negatively. We developed a new method to explore signature data for hidden structure, called divisive magnetic clustering (DIMAC). Our DIMAC approach is based on the same distance measure used in diet estimation, closely linking methods of data exploration and parameter estimation, and it does not require data transformation or distributional assumptions, as do many multivariate ordination methods in common use. We investigated the potential benefits of the DIMAC method to detect and subsequently exploit hidden structure in signature data using two prey signature libraries with quite different characteristics. We found that the existence of hidden structure in prey signatures can increase the confusion between prey types and thereby reduce the accuracy and precision of QFASA diet estimates. Conversely, the detection and exploitation of hidden structure represent a potential opportunity to improve predator diet estimates and may lead to new insights into the ecology of either predator or prey. The DIMAC algorithm is implemented in the R diet estimation package qfasar.

show abstract

Intraspecific variability in diet and implied foraging ranges of whale sharks at Ningaloo Reef, Western Australia, from signature fatty acid analysis

Cited by 23 publications

References 59 publications

Enhancing insights into foraging specialization in the world's largest fish using a multi‐tissue, multi‐isotope approach

Enhancing insights into foraging specialization in the world's largest fish using a multi‐tissue, multi‐isotope approach

Regional movements of satellite‐tagged whale sharks Rhincodon typus in the Gulf of Aden

Detect and exploit hidden structure in fatty acid signature data

Contact Info

Product

Resources

About