The world's largest omnivore is a fish.

Area of Science:

• Marine Biology
• Animal Ecology
• Biogeochemistry

Background:

• Very large body size in marine animals necessitates abundant food sources.
• Whale sharks, as secondary consumers, typically feed on nekton, which can be scarce.
• Coastal foraging requires efficient strategies targeting aggregated prey and debris.

Purpose of the Study:

• To determine the trophic level of whale sharks.
• To identify dietary components of whale sharks, particularly in coastal environments.
• To investigate the role of floating macroalgae in whale shark nutrition.

Main Methods:

• Compound-specific stable isotope analysis (CSIA) of amino acids.
• Fatty acid analysis of whale shark tissues, feces, and potential prey.
• Multi-technique approach to assess diet and trophic position.

Main Results:

• CSIA indicated a trophic level consistent with omnivory in whale sharks.
• Fatty acid profiles suggest Sargassum and its epibionts are a significant food source.
• This feeding behavior links whale sharks to oceanographic features aggregating prey and debris.

Conclusions:

• Whale sharks exhibit omnivory, incorporating floating macroalgae into their diet.
• Consumption of Sargassum provides an energetic benefit, overcoming digestion challenges.
• This foraging strategy increases whale shark vulnerability to pollutants like plastics.