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Sunday 26 August 2012

CAUGHT ON CAMERA: RARE DEEP-SEA ANGLERFISH


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Photos: Rare Deep-Sea Anglerfish Recorded
By Ker Than,
National Geographic News, 23 August 2012.

Rare Anglerfish Caught on Camera

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Floating around deep-sea rocks like a watery version of French filmmaker Albert Lamorisse’s red balloon, this bulbous, brightly coloured anglerfish was recorded by a remotely operated submarine camera off of California’s Central Coast in 2010.

While scientists have observed other species of anglerfish in the wild before, this particular species - Chaunacops coloratus - wasn't documented alive until 2002, explained Lonny Lundsten, a researcher at the Monterey Bay Aquarium Research Institute (MBARI).

The 2002 sighting was of a single fish found near a seamount, or extinct volcano, about 80 miles southwest of Monterey. In 2010 an expedition to the nearby Taney Seamounts found six more - enough to support a proper investigation of the species.


In a new study - published in the journal Deep-Sea Research Part I - Lundsten and his colleagues describe the first observations of the rare fish in its natural habitat. C. coloratus, which can “walk” and changes colour throughout its life, was found nearly 11,000 feet (3,353 meters) below the surface.

Red Fish, Blue Fish

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The first live observations of anglerfish in their natural habitat revealed that not all of them are red or rose-coloured, as previously thought.

"One of the things we noticed right off the bat is all the larger ones are red and the smaller ones tend to be blue," MBARI's Lundsten said. "So we think ... that it's changing colour, from a bluish-transparent larval phase to a red adult form."

The largest specimen that Lundsten's team observed was about 8 inches (20 centimetres) long, while the smallest was about 3 inches (7 centimetres) long.

The purplish colour of the anglerfish pictured above suggests it is an adolescent, Lundsten added.

Another surprise from the imagery Lundsten's team collected: The fish appear able to "walk" along the seafloor using a combination of their pectoral fins and pelvic fins.

Scientists speculate that “walking” is more energy efficient than swimming short distances, and that it also disturbs the surrounding seawater less, reducing the chances of startling nearby prey.


Strong Swimmer

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Yellow sediments cling to the fins of an adult deep-sea anglerfish photographed swimming near the Taney Seamounts, off California’s Central Coast at a depth of about 8,530 feet (2,600 feet).

C. coloratus was first described from a single dead specimen, which was collected at the Cocos Ridge in the Pacific Ocean near Costa Rica in 1891, but it had never been seen alive by scientists.

That changed in 2002, when the remotely operated vehicle (ROV) Tiburon stumbled upon the species near Davidson Seamount, also off the coast of California.


In 2010, the team observed six more of the rare fish during ROV dives at Taney Seamounts.

The ROV footage revealed that C. coloratus can live at depths of up to 11,000 feet (3,353 meters) - nearly twice as deep as previously thought.

(More about deep-sea exploration: “James Cameron Completes Record-Breaking Mariana Trench Dive.”)

Waiting for Prey

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A deep-sea anglerfish hides among rocks as it waits to ambush curious fish. On its head is a piece of dangling flesh - called an "esca" - that functions as a lure for prey.

"They're ambush predators," MBARI's Lundsten explained. "If something comes by, they'll open up their huge mouths and swallow up whatever it is."

(See more ocean-species hunting tricks: “Photo Gallery: Masters of Undersea Camouflage.”)

During one ROV dive, the researchers observed an anglerfish stowing its fishing gear away in a special cavity located between its eyes.

Lundsten and his team suspect that C. coloratus's lure glows in the dark to better attract prey, but this has not been confirmed.

"We didn't observe any bioluminescence [in the ROV video] ... but we assume that it probably does," he said.

[Source: National Geographic News. Edited.]


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