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NOAA Project Team Encounters Monk Seal at Astounding Depth

On a recent research voyage conducted by the National Oceanic and Atmospheric Administration (NOAA) in the Northwestern Hawaiian Islands (NWHI), scientists had a surprise encounter with a monk seal at a depth of over 1,600 feet. The mission, conducted by NOAA’s Office of Ocean Exploration, is designed to investigate how endangered Hawaiian monk seals use shallow and deep-water habitats for hunting and protection. NOAA is an agency of the U.S. Department of Commerce.

Frank Parrish, a fishery biologist with NOAA’s Pacific Island Fisheries Science Center, was on the lookout for Hawaiian monk seals when he sailed with a multidisciplinary team of scientists on the University of Hawaii's Research Vessel Ka'imikai-o-Kanaloa (Heavenly Searcher of the Seas). Scientists were supported by Hawaii Undersea Research Laboratory (HURL) and its deep-sea manned submersibles Pisces IV and V, a remotely operated vehicle (RCV-150) and a Seafloor Sonar Mapping System.

“In previous studies, monk seals had been tagged to signal a satellite when they surfaced, and we found they were showing up in clusters,” said Parrish. “Some clusters were easily explained, but some were distant with only the deep ocean below. Those areas were ripe for exploration.” Parrish surmised that monk seals clustered over deep ocean seamounts populated with a diverse community of deep-sea coral and other invertebrates, and used the corals as reference points for foraging in the area, or as a habitat for feeding.

“We know gold coral fluoresces when something brushes against it,” said Parrish. “If an eel or other food source in coral is disturbed by a monk seal, the coral ‘lights up’ and that could be like ringing the dinner bell for a monk seal.”

In 1998, National Geographic deployed research cameras, or “Crittercam”, on Hawaiian monk seals. “We saw what the seals saw as far as light penetrated the ocean to about 300 meters in what’s called the ‘photic’ layer,” said National Geographic’s Patrick Greene. On this expedition we hoped to document a connection between monk seals and deep ocean coral communities,” he said.

On a dive below 500 meters (approximately 1,640 feet), the submarine’s lights lit up the area as Amy Baco-Taylor from Woods Hole Oceanographic Institution and HURL’s submersible pilot, Terry Kerby, prepared to collect corals growing on the side of vertical carbonate wall

The sub fought a strong and persistent current trying to set its port side hard into the wall. Kerby powered the thrusters to gently set the sub against the wall and let the current move the sub down the wall until he steadied the sub on the edge of a specimen collection box. Co-pilot Max Cramer took the thruster controls to hold the sub in this precarious position while Kerby positioned a camera and used the sub’s mechanical arm to pluck a twig from a precious coral tree and stuff it into a jar in the specimen box.

“From the submarine’s portside viewport, I noticed some movement,” said Cramer“In a fraction of a second the shadow filled the entire viewport, about six inches from my dropping jaws. ‘It’s a monk seal,’ I hollered, firmly believing I’d be the only one to see the magnificent animal at a depth, and in a deep-sea coral field, as never before witnessed.”

Kerby and Baco-Taylor snapped their heads to their viewports. “I couldn’t believe it,” said Baco-Taylor. “I thought he was joking. Then I saw him. He had just looked into Terry’s viewport, then swam a little further and looked into my viewport at me! He showed no sign of stress if he was out of his depth range, He was clearly comfortable and took his time checking us out,” she said“I saw the mark A-12 very clearly before he swam away.”

A-12 was tagged this summer on Lisianski Island in the NWHI chain as part of NOAA’s National Marine Fisheries Service’s protected species investigation, and was observed about 350 miles from where the animal was tagged.

“I believe it’s the first time a monk seal was seen to be associated with deep-sea precious corals and the first time a monk seal was seen from a submarine at such a depth,” said Parrish.

Monk seal in Hawaiian is “ilio-holo-kai” or “the dog that runs in the sea.” There are only three known species of monk seals, the most primitive of pinnipeds. The Caribbean monk seal is extinct. About 500 Mediterranean monk seals and 1,200 to 1,400 Hawaiian monk seals are listed as endangered.

NOAA's Office of Ocean Exploration coordinates and funds interdisciplinary voyages of discovery to map and explore the ocean at new scales, develop a more thorough understanding of ocean dynamics and interactions, develop new sensors and systems, and share the excitement of discovery with the public. Outreach and education activities associated with NOAA-sponsored missions to the NWHI include K-12 lesson plans, mission summaries and explorer biographies on NOAA’s Office of Ocean Exploration Web site.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of our nation's coastal and marine resources.

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