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Marine Ecology Progress Series

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MEPS 632:159-174 (2019)  -  DOI:

Trophic niches determined from fatty acid profiles of sympatric coral reef mesopredators

Stacy L. Bierwagen1,2,*, Heidi Pethybridge3, Michelle R. Heupel4, Andrew Chin1,4, Colin A. Simpfendorfer1

1Centre for Sustainable Tropical Fisheries and Aquaculture and College of Science and Engineering, James Cook University, Townsville, QLD 4810, Australia
2AIMS@JCU, James Cook University, Townsville, QLD 4810, Australia
3CSIRO, Oceans and Atmosphere, Hobart, TAS 7001, Australia
4Australian Institute of Marine Science, Townsville, QLD 4810, Australia
*Corresponding author:

ABSTRACT: Previous research has identified similar trophic levels in a wide range of coral reef sharks and large teleost fishes but has been unable to resolve the extent of dietary overlap and resource sharing that lead to interpretation of functional roles and, hence, adequately describe interaction strengths in food webs. We used fatty acid (FA) profiles of muscle and plasma reflecting the diet of several mesopredators to better understand the trophic structure and functioning of Great Barrier Reef ecosystems. Multivariate analysis identified significant dietary overlap between 2 shark species (whitetip reef shark Triaenodon obesus and grey reef shark Carcharhinus amblyrhynchos), but whitetip reef sharks occupied a smaller niche area than grey reef sharks. We also found clear niche separation between sharks and teleost fishes (red throat emperor, coral trout, and grass emperor). All mesopredators sampled had high proportions of polyunsaturated FAs linking them to carnivory, but differences among species in trophic biomarker ratios suggest distinctive dietary sources. However, based on a degree of niche overlap of species sharing common diet, reef-dwelling teleost fishes such as coral trout also derive nutrients from pelagic environments. A faster analytical method to determine FA profiles, proven highly useful in tuna, was tested and deemed viable for muscle tissue of tropical teleost fishes and sharks, while questions remain for use of FA extraction of plasma in ecological studies. These results demonstrate that fine-scale inter-specific differences in diet exist between mesopredators in coral reef ecosystems. Our results raise important questions about the ecological influences of these species and energy flow among mesopredators in coral reef ecosystems.

KEY WORDS: Ecological niche · Dietary overlap · Fatty acids · Reef sharks · Mesopredators

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Cite this article as: Bierwagen SL, Pethybridge H, Heupel MR, Chin A, Simpfendorfer CA (2019) Trophic niches determined from fatty acid profiles of sympatric coral reef mesopredators. Mar Ecol Prog Ser 632:159-174.

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