As originally reported by Live Science, the world's largest fish, whale sharks, might be migrating to the Azores as a result of global warming. Recent tracking shows these ocean giants are increasingly using this chain of volcanic islands off the western coast of Europe in response to rising sea temperatures. What’s more, this recent finding could be essential to the future of whale sharks and countless other species, shedding light on how climate change might alter fish behaviour worldwide.
Whale sharks are gentle giants, known to reach an incredible 12 metres in length and over 20,000 kilograms in weight, and some scientific evidence suggests they can grow even larger. Incredibly, this supersized species survives almost entirely on one of the ocean's most minuscule organisms - plankton. They use rows of tiny teeth as a filter to strain these barely-visible bug-like creatures out of the seawater, similarly to baleen whales.
Whale sharks can be found all over the world and prefer warm tropical waters between 26 and 30 degrees Celsius. However, in recent years, their migratory patterns seem to be changing. Local fishermen have increasingly sighted these massive fish around the Azores Islands - nine volcanic specks in the vast northern Atlantic west of Portugal. This region lies along the colder northern edge of waters that whale sharks have historically preferred.
To better understand why these ocean titans are appearing more often around the Azores, scientists analyzed data on whale shark sightings gathered over 16 years. These detailed records were collected by observers on tuna fishing boats from 1998 to 2013. Traditional fishermen in the Azores have detected tuna by looking for whale sharks for centuries, but nobody - not even the fishermen - knows exactly why the sharks are so commonly joined by small schools of tuna.
To try and understand the patterns of whale shark sightings, researchers then used computer models capable of comparing external factors. Considerations included food, sea surface temperatures, and seafloor features. This investigation showed a sharp rise in whale shark sightings during the exceptionally warm year of 2008. And, by the look of it, the sharks then stayed and many individuals have since become regular visitors to the region.This same research indicated that sea surface temperatures could help predict whale shark sightings. The sharks were observed in the region's warmest waters, around the southernmost Azores Island of Santa Maria. Observers also noticed that the sharks seem to prefer areas with underwater pinnacles and mountains. These subaquatic seafloor features play a role in forcing nutrient-rich upwellings to the surface, loaded with the photosynthetic organisms that whale sharks like to eat.
These findings are big news, and not only when it comes to whale sharks. They could be a glimpse of what's to come as the climate changes globally. Large marine animals of all kinds may be forced to change their oceanic distributions and migratory patterns depending on regional conditions.
Scientists in the Azores have their sights set on solving other local whale shark mysteries. Up next, they hope to investigate why whale sharks remain in the area during the summer. Is it only the food around the seamounts, or something else - perhaps the presence of other whale sharks to mate with?
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