Chemical Ecology Studies May Reveal How Whale Sharks Find Food

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While little is known about the world’s largest fish, most experts agree that whale sharks are usually solitary creatures. But each summer these amazing marine fish migrate great distances to select feeding aggregation sites. But how do they find food in the vast ocean? Chemical ecology studies may soon answer this puzzling question.

Georgia Aquarium field researchers are currently studying chemical interactions in an area of the Yucatan Peninsula known to many locals and biologists simply as ‘afuera.’ Their most recent studies involve analyzing chemical interactions between the afuera whale shark aggregation and nearby plankton populations.

Unique technology enables researchers to collect and seal water samples at predetermined depths. Below, Dr. Alistair Dove, Senior Scientist at the aquarium explains how the equipment is used for chemical ecology testing.

“We are interested in chemical ecology because it is the study of chemical interactions – chemical production and chemical signaling – between living organisms,” says Harry Webb, Senior Laboratory and Research Technician at the Georgia Aquarium.

Below, Webb and Dove submerge the niskin sampler into the ocean and begin the water sampling process:

After collection, the water is processed utilized various techniques and equipment, such as a portable pH meter, dissolved oxygen meter and a gas Chromatograph/mass spectrometer. “Our water quality and diagnostic lab has many powerful tools to analyze the water collected from samples in the afuera area,” says Webb. “We look for potential chemical signals that help us to understand why the whale sharks gather in the same spot year after year.” Analyses of the water samples will also take place at the UNAM campus in Sisal, at the lab of Santiago Capella Vizcaino, with whom the aquarium collaborates. 

Could it be that whale sharks are sensitive to a specific chemical in the water, giving them the ability to ‘smell’ abundant fish eggs from hundreds of miles away? Scientist Dove says that the “concentration of odor chemicals – DMS/DMSO and DMSP – should be higher offshore,” but water sample testing will help verify their theory.

Learn more about whale sharks by checking out my case study on research in the Gulf of Mexico.

Video Credit: Jodi Kendall

Photo Credits: Georgia Aquarium