Fifteen whale species were spotted during a recent scientific deep-sea expedition carried out by Chinese researchers in the northern waters of the South China Sea.

A team of researchers from the Marine Mammal and Marine Bioacoustics Laboratory of the Institute of Deep-sea Science and Engineering under the Chinese Academy of Sciences (CAS) conducted the scientific expedition which aimed to conduct research on the diversity, population levels and distribution patterns of whales in the South China Sea.

The 20-day expedition, having covered over 3,500 kilometers, wrapped up on July 15 in Sanya City, south China's Hainan Province.

During the trip, they observed at least 15 whale species including 10 deep-diving whale species and spotted five dolphin species living far out at sea.

"We collected 43 acoustic recording samples and recorded acoustic signals from about 15 species of marine mammals, which has enriched our base of acoustic data from the South China Sea," said Dong Lijun, assistant researcher with the Institute of Deep-Sea Science and Engineering under the CAS.

"We discovered a mysterious beaked whale that had never been found in previous voyages," he said.

This latest scientific expedition provides further evidence of the rich whale biodiversity within the surveyed waters. As a flagship species of marine ecosystems, whales are indicative of the local environmental conditions and of great research value for better protection of the ecological environment in the South China Sea, the researchers said.

Starting in 2019, the laboratory has carried out six scientific expeditions in the South China Sea for five consecutive years. So far, more than 30 cetacean species have been discovered during a total of six research expeditions. (CGTN)