An explosion in the numbers of alien mussels in the Thames could threaten the river's native species.

A survey of wildlife living in the Thames between Wallingford and Richmond found massive numbers of zebra mussels - a species native to south-east Russia.

The highest number of the creatures were discovered living on stretches of the river from Walton-on-Thames to Teddington.

Scientists have warned the foreign muscles could displace native species, especially the depressed river mussel, listed as a priority for conservationists.

The tiny mussel, named after their stripy shells, often cling together and block outlet pipes and Thames Water has been forced to hire specialists to chip them off the capital's water pipes.

An adult female zebra mussel is one of the most reproductive organisms in the world. It can produce between 30,000 and 40,000 eggs per year.

Dr Jean Luc Solandt, biodiversity policy officer for the Marine Conservation Society said: "We are basically concerned that the level of zebra mussel invasion in UK waters at present could precipitate the same effects on native ecology and industry as seen in the Great Lakes which has cost industry millions of US dollars."

This is not the first alien species to be found near Richmond. In 2006 scientists noticed an abundance of juvenile Chinese mitten crabs.

Dr Solandt added: "The major effects of these species can be ecological (they out compete native species), economic (they clog up water inlets, mooring buoys and ships hulls). There are two currently know major vectors of these animals and plants - one is where they come in stuck on the hulls of ships, the other is where they are in the form of larvae in the ballast water of large cargo ships."