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The world’s largest omnivore is a fish


Meekan, MG and Virtue, P and Marcus, L and Clements, KD and Nichols, PD and Revill, AT, The world's largest omnivore is a fish, Ecology, 103, (12) Article e3818. ISSN 0012-9658 (2022) [Refereed Article]

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Copyright 2018 Ecological Society of America

DOI: doi:10.1002/ecy.3818


The evolution of very large body size requires a ubiquitous and abundant source of food. In marine environments the largest animals such as whale sharks are secondary consumers that filter feed on nekton, which is plentiful, although patchy. Consequently, feeding in coastal environments requires cost-efficient foraging that focuses on oceanographic features that aggregate both nektonic prey and marine debris such as floating macroalgae. Consumption of this algae could present an energetic challenge for these animals, unless some component can be digested. Here, we use a multi-technique approach involving amino acid compound-specific stable isotope analysis (CSIA) and fatty acid analysis to determine the trophic level of whale sharks and to identify likely items in the diet. CSIA analyses showed that the species has a trophic level consistent with omnivory. Fatty acid profiles of whale shark tissues, faeces and potential prey items suggest that the floating macroalgae, Sargassum, and its associated epibionts is a significant source of food. Although this overcomes the energetic challenge of consumption of floating algae, this mode of feeding and the need to focus on oceanographic features that aggregate prey also increases the threat to the species posed by pollutants such as plastic.

Item Details

Item Type:Refereed Article
Keywords:biochemical, diet, filter feeding, herbivory, macroalgae, Rhincodon typus
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Marine biodiversity
UTAS Author:Virtue, P (Associate Professor Patti Virtue)
UTAS Author:Marcus, L (Ms Lara Marcus)
UTAS Author:Nichols, PD (Dr Peter Nichols)
ID Code:151194
Year Published:2022
Web of Science® Times Cited:1
Deposited By:Ecology and Biodiversity
Deposited On:2022-07-25
Last Modified:2023-01-23

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