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Deep-sea shark species spotted in waters of Palau and Solomon Islands for the first time

Shark in the water
Pacific sleeper shark/Photo courtesy of PICRC

By Pacific Island Times News Staff

Koror— A shark species previously thought to inhabit only as far south as Taiwan has been spotted for the first time in the waters of Palau and the Solomon Islands, according to a paper recently published in the Journal of Fish Biology.

The Pacific sleeper shark was observed to the east of Babeldaob at 1,288 meters depth during research undertaken in 2021 by the Palau International Coral Reef Center and the National Geographic Society.

During a 2015 expedition, a large sleeper shark was observed in the Solomon Islands at 937 m, 20 km east of Kavach, according to the report published on June 20.

Sleeper sharks (Somniosus pacificus) are large deep-water sharks that live at depths of up to 2,000 meters. The paper presented the first observation of this species in the western Pacific tropics, extending its range about 2,000 nautical miles south.

The authors said the observations provided much-needed information on the range of the species and can help guide future management and conservation actions.

“On both expeditions, the individuals were dark grey to blackish in color with white/grey spots. They had a large, cylindrical heavy-bodied shape characteristic of the three large known Somniosus species, with a short, rounded snout and a thin-lipped, nearly transverse mouth,” the report said.


“The spineless dorsal fins were equal sized and low. The pectoral fins were short and rounded at the rear tips. The caudal peduncle was short, and the caudal fin heterocercal in shape, with a long lower lobe and short upper lobe.”

Technological advances have enabled scientists to expand ocean exploration further into the deep, thus providing new discoveries and species observations.

The sleeper sharks were spotted in Palau and the Solomon Islands through a deep-sea camera system provided by the National Geographic Society’s Exploration Technology Lab.

PIRC said prior to the expedition sleeper sharks were mainly seen from strandings or due to by-catch. Their range was thought to extend from Taiwan in the south to within the Arctic Circle in the north.

“A greater understanding of the range of this species, which is classed as ‘near threatened’ according to the IUCN Red List, will help guide future conservation action,” said first author, Dr. Louw Claassens, former researcher/ science Officer at PICRC.

“These deep-sea camera systems have allowed us to gain a better understanding of what lives in Palau’s deep ocean, which still remains very much a mystery,” Claassens said.

The deep-sea camera system, capable of descending to 6,000 meters, was deployed for a total of three hours in Palau.

The sleeper shark in Palau’s waters was seen after two hours and 17 minutes, and was in and out of view for the remainder of the time, according to the report.

The shark, later deemed to be an adult male, interacted with the camera and bait canister—bumping into the camera and moving it.

PICRC said the sleeper shark sightings in Palau and the Solomon Islands hinted at the possibility that the areas of the ocean where they were found contain more unreported species.

A previous study reported that Palau’s pelagic fauna is both diverse and rich with many different species of fishes found at thousands of meters of depth.

PICRC said continued deep-sea exploration will allow for a better understanding of Palau’s pelagic environment and the animals, like the Pacific sleeper shark, that inhabit it.

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