Hong Kong  - A Hong Kong park was preparing on Thursday to send two sick rare sturgeon back to China for treatment after the death of three other fish, all gifts from the Beijing government.

The two endangered fish will be moved from Ocean Park to the Yangtze River Fisheries Research Institute in Xiamen where experts will try to save them following a decision by mainland authorities to take them back.

An Ocean Park spokesman said it was unknown whether the fish would be returned if they recovered.

The incident is acutely embarrassing to Hong Kong, which was given five Chinese sturgeon last June as a gift to mark China's staging of the Olympic Games. Each fish represented one of the Olympic mascots.

Within days of their arrival one fish was savaged by a barracuda and died.

Hong Kong's leader Donald Tsang made a grovelling public apology for the three year-old sturgeon's death while Chinese officials were drafted in to advise Ocean Park on how to care for the other fish. Beijing then sent five more.

But in December, a second fish died from a bacterial infection, followed by the third weeks later from a wound.

The two sick fish, both nine years old, will be transported overland to the research centre in China Friday, the park spokesman said, leaving five live sturgeon at the park's sturgeon aquarium which is currently closed to the public.

It is believed the illness and deaths could be linked to an adverse reaction to the salinity of the water.

The fish will be cared for by experts at The Yangtze River Fisheries Research Institute of the Chinese Academy of Fisheries Sciences which is home to a breeding programme aimed at protecting the sturgeon.

The Chinese sturgeon can grow up to 4 metres long and is believed to date back to the time of the dinosaurs. It is strictly protected by the Chinese government which regards it, like the panda, as a national treasure.

Hong Kong reverted to Chinese rule in 1997 after 156 years as a British colony. The city of 6.9 million hosted the equestrian events of the Beijing Olympics for which the sturgeon was a mascot. (dpa)