Evidence for inter- and intraspecific trophic niche separation among deepwater elasmobranchs on the southern Great Barrier Reef, Australia

Munroe, Samantha E.M., Rigby, Cassandra L., and Hussey, Nigel E. (2020) Evidence for inter- and intraspecific trophic niche separation among deepwater elasmobranchs on the southern Great Barrier Reef, Australia. Marine Ecology Progress Series, 636. pp. 107-121.

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View at Publisher Website: https://doi.org/10.3354/meps13221


Abstract

Quantifying the trophic structure and interactions of deepwater (>200 m depth) elasmobranch assemblages is required to improve our understanding of deepwater ecosystems and the impacts of increased deepwater exploitation. To this end, we investigated the trophic ecology of deepwater elasmobranchs on the Great Barrier Reef (GBR) using a stable isotope (delta C-13 and delta N-15) approach. Our study included 4 species captured in the southern GBR deepwater eastern king prawn trawl fishery: the eastern spotted gummy shark Mustelus walkeri, the piked spurdog Squalus megalops, the pale spotted catshark Asymbolus pallidus, and the Argus skate Dentiraja polyommata. The delta C-13 and delta N-15 values of all 4 species ranged from -18.6 to -16.2 parts per thousand and 8.3 to 13.8 parts per thousand, respectively. The small C-13 range was likely due to the limited number of unique carbon baseline sources typically found in deepwater environments. Despite this, 3 of the 4 species exhibited relatively low core (40% SEA b ) isotopic niche overlap (<1 to 44%). Isotopic niche separation may be driven by multiple interacting factors including morphology, feeding strategies, or resource partitioning to reduce competition. Isotope analysis also provided evidence for intraspecific variation; S. megalops, D. polyommata and M. walked exhibited significant increases in delta N-15 (similar to 3 parts per thousand) and delta C-13 (similar to 2 parts per thousand) with size. Latitude, longitude, and depth had statistically significant but comparatively minor effects on isotope values (<= 1 parts per thousand) of the 4 species. Cumulatively, our results indicate that isotopic variation among deepwater elasmobranchs on the GBR is principally driven by size and species-level differences in resource use.

Item ID: 62836
Item Type: Article (Research - C1)
ISSN: 1616-1599
Keywords: Elasmobranchs, Deepwater, Stable isotope analysis, Great Barrier Reef
Copyright Information: © Inter-Research 2020
Funders: Save Our Seas Foundation (SOSF)
Date Deposited: 15 Apr 2020 07:38
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 100%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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