SCIENTISTS have observed great white sharks flocking to a deep and mysterious region of the ocean.
A new study found that 12 species of large predatory fish, including great white sharks regularly spent time in the mesopelagic zone.
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This is also known as the ocean’s twilight zone and it measures between the depths of 656 and 3,280 feet.
The mesopelagic zone occupies about 60% of the planet’s surface and around 20% of the ocean’s volume.
The predatorial fish were also found frequenting the midnight zone, which is 3,280 to 9,800 feet beneath the ocean surface.
“How, when, where they access the deep ocean certainly varies, but the clear anecdotal answer is that the deep ocean seems like an important habitat — regardless of the predator species,” Camrin Braun, study lead and an assistant scientist at the Woods Hole Oceanographic Institution (WHOI), told Live Science.
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“It’s clear there are good reasons for these animals to dive deep, otherwise why would they all do it?”
The study was published on November 6 in the journal PNAS.
For their research, the team looked at the diving patterns of 344 predatory fish, including great white sharks, which they electronically tagged.
They used shipboard sonar over 46,659 days to identify which species often deep dive into the twilight and midnight zones.
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The study revealed a link between the depths reached by the dives and the position of the deep scattering layer (DSL), Live Science reported.
The National Oceanic and Atmosphere Association (NOAA) describes the DSL as “an area of high concentration of marine organisms that live suspended in the water column.”
Many of these organisms, including fish, have swimbladders that can reflect sound.
They can reflect the sound so strongly that the layer is often mistaken for the seabed.
Organisms in the DSL feed at night closer to the surface, and then return to the twilight zone in the day.
“There’s good evidence for some species/situations in which diving deep is clearly for foraging,” Braun said.
“So that supported our expectation. However, we also find several cases where we can pretty definitively say the use of the deep ocean is not for feeding — or if it is it represents a totally different kind of predator-prey interaction or mysterious prey resource.”
The research also indicates that the Twilight Zone has been disregarded as a crucial habitat for large predator species.
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