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The largest living fish, whale sharks, may increasingly be using volcanic islands off the western coast of Europe as a new home as sea surface temperatures rise, researchers say.
This finding could shed light on how climate change might alter the behavior of fish globally.
The whale shark is a titan, known to reach up to 41.5 feet (12.65 meters) in length and 47,000 pounds (21,500 kilograms) in weight. Unlike great white sharks, whale sharks are gentle giants, using rows of teeth as a filter to strain out tiny creatures in the water for meals.
"Whale sharks are the largest living fish, yet they are also very elusive," said Pedro Afonso, a marine and fisheries ecologist at the University of the Azores.
Whale sharks prefer warm tropical waters that are 79 to 86 degrees Fahrenheit (26.5 to 30 degrees Celsius). However, in recent years, fishermen have increasingly sighted these giant fish around the Azores Islands, nine volcanic isles in the central North Atlantic west of Portugal. These islands lie along the colder northern edge of the waters that whale sharks historically have preferred. [Image Gallery: Mysterious Lives of Whale Sharks]
To better understand why these gargantuan fish appear more often around the Azores, the scientists analyzed data on whale shark sightings gathered over 16 years, from 1998 to 2013, by observers on tuna fishing boats. Fishermen in the Azores have long detected tuna by looking for whale sharks.
The researchers found a sharp rise in whale shark sightings in the exceptionally warm year of 2008, and the giant fish became regular visitors to the region afterward. The scientists also found that sea surface temperatures helped predict whale shark sightings.
Afonso and his colleagues Niall McGinty and Miguel Machete detail their findings this week in the journal PLOS ONE.