BEIJING, June 15 (Xinhua) -- Cetaceans, such as whales and dolphins, in the South China Sea are at risk of disappearing amid overfishing, scientists warn in an article recently published in the journal Science.

A fishing boat returns to harbor in Qionghai, Hainan Province on May 1. China started a three-month fishing moratorium on South China Sea on 12:00 May 1. (File photo by CFP)

Li Songhai, lead author of the article and researcher from the Institute of Deep-sea Science and Engineering, under the Chinese Academy of Sciences, researched cetaceans in the South China Sea last year. Li's team found that this sea region had high cetacean species diversity, but the marine animals there had been overlooked.

Overfishing, together with other human activities, is putting cetaceans in danger, the article said.

Cetaceans are large mammals, but overfishing has limited their nutrition as they now have little prey to eat. Fishing operations have also caused hundreds of cetaceans to be caught by mistake or hit by fishing vessels, resulting in casualties.

Furthermore, many fishing vessels produced underwater noise that damaged cetaceans' hearing and disturbed their behavior.

"If no conservation actions are taken, cetaceans would disappear from the South China Sea," Li said, adding that saving the animals is an urgent priority for maintaining marine biodiversity and ecosystems.

In the article, the scientists suggest that regional countries carry out research to investigate and identify key cetacean areas in the South China Sea, where fishing and other human activities will be strictly controlled.

Li's team also called on regional countries to cooperate on fisheries management and launch national action plans against illegal, unreported and unregulated fishing, to protect vulnerable cetaceans from harm.