The Hidden Life of Sharks: Surprising Discoveries in the Deep Sea

KOMPAS.com – Some sharks will occasionally be seen breaking through the water at the surface of the sea.

But this brief and amazing moment turns out to be only a small part of the picture of this carnivore’s life.

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Often sharks and other large marine predators disappear and remain unseen, raising the question of where do they go?

Collect Phys, Wednesday (8/11/2023) a new study showed that large predatory fish such as sharks, tuna and billfish made surprising visits to the deep sea, especially the mesopelagic zone, which is located between 200 and 1,000 meters below the surface.

Previously, the area, also known as the ocean’s twilight zone, had been overlooked as an important habitat for large predatory species.

“No matter what apex predator you see, or where you see it in the global ocean, they all spend time in the deep sea,” said Camrin Braun, assistant scientist at the Woods Hole Oceanographic Institution (WHOI).

“All the animals that we think of as surface-dwelling seas use the deep sea more than we previously thought,” he explained.

This finding was obtained after scientists analyzed data from 344 tags or electronic tags during 46,659 days of tracking for 12 species in the North Atlantic Ocean, including white sharks, tiger sharks, whale sharks, yellowfin tuna, swordfish and many more.

The diving patterns of these fish recorded by the tags were then matched with sonar data showing the daily movement of the deep scattering layer (DSL).

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This is a zone where a number of small fish and marine organisms gather very densely.

During the day, animals in the DSL inhabit the mesopelagic zone. Then when the sun sets, many individuals such as fish, molluscs, crustaceans, swim to the surface of the water to look for food. This daily rhythm is called Diel Verticle Migration.

Reasons to dive into the deep sea

The Diel Vertical Migration Pattern explains why predators dive into the depths of the sea, namely to look for food in the DSL area which is full of fish.

However, Braun found that there was behavior that was not only for looking for food. For example, swordfish dive to depths of 3000 feet or 6000 feet, much deeper than their feeding behavior.

That means they may be diving for other reasons that are not yet fully understood. Previous research has shown that these dives function to avoid other animals or aid navigation.

“Sharks and tuna are evolutionarily very different and have very different sensory systems. Yet both groups still find deep-sea diving behavior beneficial,” said Simon Thorrold, a fish ecologist at WHOI and one of the study’s authors.

With so many fish and organisms making this journey, Thorrold said that these species have the potential to move large amounts of carbon dioxide from the surface to the deep ocean where it will remain for centuries, which is useful for the ecosystem.

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This provides insight that the mesopelagic layer provides important support for the ocean.

The scientist added that if you start exploiting the ecosystem before knowing how it works, there is a big risk that it could cause damage that is not easily repaired.

The study was published in the journal Proceedings of the National Academy of Sciences.

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2023-11-13 05:33:00
#Marine #Predators #Dive #Dark #Bottom