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Chilean devil rays (Mobula tarapacana) are one of the most charismatic fish believed to reside at the surface water in the ocean. However a new study has revealed the unusual and impressive travel patterns of devil rays, that says that the fish make surprisingly fast and deep dives into the Atlantic Ocean nearly straight down at 13 miles per hour.
Very less is known about this species. Their movement and feeding patterns has always been a bit of a mystery.
The front part of the animal’s skull is stuffed with a small and soft mesh of large and small arteries called a rete mirabile, and was described in the devil rays 30 years ago. The research says the devil rays use their rete mirabile to warm up their brains before making a deep dive to search for food in the ocean’s depths.
The team, led by Simon Thorrold of Woods Hole Oceanographic Institute in Massachusetts, tagged and tracked 15 devil rays in 2011 and 2012 off the coast of the Azores—Portuguese islands in the middle of the North Atlantic Ocean for up to nine months.One of the deepest and fastest divers in the ocean traveled across great distances—up to 49 kilometers (30 miles) per day, and as far as 3,800 kilometers (2,300 miles) over several months time.
“It was a mystery as to why they had this system, which is a way of keeping brain activity high, even in a cold environment,” said Thorrold, a biologist at WHOI.
“So little is known about these rays,” added Thorrold. “We thought they probably travelled long distances horizontally, but we had no idea that they were diving so deep.”
“That was truly a surprise,” said Thorrold — a surprise that explains the need to keep the brain extra warm.
The tags which are programmable gadgets recorded depth, light, temperature and position data for up to five months, before detaching themselves and bobbing to the surface, where they beamed their data back to the researchers via satellite.
Post tagging the fish disappeared in the autumn. “We had no idea where they were going,” said Dr Thorrold. “We had an idea that they were moving a long way, perhaps several thousand kilometres.”
Then came in play the tags.
“The first thing I looked at was the temperature data,” said Dr Thorrold, “and I saw temperatures of about 4C – and this is an animal that’s supposed to be living in the tropics! I suspected there was probably a mistake.”
“With those kinds of low reproductive rates, any type of mortality is going to have a big impact on the species,” Thorrold said in a press release. “We don’t know enough about devil rays to even know if we should be worried about their status. There are lines of evidence to suggest we ought to be worried, or at least that we should be trying to learn more about the biology and ecology of these rays.”
These rays, in effect, connect the surface, epipelagic layers in the ocean, with the deep — the twilight zone,” said Thorrold.
And this connection could offer new clues to the health of the oceans as a whole.
“Ultimately, answering whether these animals depend on the deep layers of the ocean for their feeding and survival could have major implications for their management and that of oceanic habitats,” said co-author Pedro Afonso, a researcher from the University of the Azores.
The new study was published this week in the journal Nature Communications.