Whale Shark Highways
Photo: Galapagos Whale Shark Project
Unknown to most, August 30th is International Whale Shark Day. While whale sharks are charismatic animals and are important for tourism in many island communities, we still know little about their behavior and movements in the ocean. In a new study published in PlosONE, researchers at the Monterey Bay Aquarium Research Institute describe their recent observations of whale shark movements in the Eastern Tropical Pacific.
Whale sharks are the largest fishes on Earth and travel long distances to feed on planktonic organisms like copepods or small fish. Researchers have long tried to understand where whale sharks move throughout the ocean, which is necessary to inform conservation efforts. For the first time, researchers at MBARI used satellite tags to track the movements of 27 whale sharks northwest of the Galapagos islands in the Eastern Tropical Pacific. The satellite tags remained on the whale sharks for four to six months and the data obtained from these tags provided insights on where the sharks travel to locate prey or mate.
The researchers used the tag data to understand how movement patterns were related to oceanographic conditions, including temperature. They found that the movement patterns consistently followed frontal boundaries between warm and cold water. In the Eastern Pacific, this boundary is known as the North Pacific Equatorial Upwelling Front. To the north of this boundary is warmer, less productive water and to the south are cooler, more productive areas. Whale sharks may choose to travel along this transition zone to optimize feeding and physiological needs. This information is important to estimate population locations and predict the movements and behaviors of whale sharks.
John P. Ryan, Jonathan R. Green, Eduardo Espinoza, Alex R. Hearn. Association of whale sharks (Rhincodon typus) with thermo-biological frontal systems of the eastern tropical Pacific. PLOS ONE, 2017; 12 (8): e0182599 DOI: 10.1371/journal.pone.0182599