A freshwater dolphin found only in China is now "likely to be extinct", a team of scientists has concluded.

The researchers failed to spot any Yangtze river dolphins, also known as baijis, during an extensive six-week survey of the mammals' habitat.

The team, writing in Biology Letters journal, blamed unregulated fishing as the main reason behind their demise.

If confirmed, it would be the first extinction of a large vertebrate for over 50 years.

The World Conservation Union's Red List of Threaten Species currently classifies the creature as "critically endangered".

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