Thames River invaded by aliens

Scientists from ZSL, Thames Landscape Strategy and the Marine Conservation Society expect to find a number of "alien" species from as far away as China, along with rare native species which may be being affected by these "invaders".

The weirs at Richmond Lock were lifted on Sunday to allow the Port of London Authority to carry out essential maintenance works on the lock, weirs and sluices until November 25th. The weir being lifted allows the river between Richmond Lock and Teddington Lock to drain naturally at low tide and creates this short annual opportunity to access the lower shore for surveys.

Conservationists will use this three-week window of opportunity to record as many native and non-native species as possible. ZSL will be continuing its survey from last year to record all species living in and on the riverbed and the MCS will be concentrating on non-native invasive species. The teams expect to find the non-native Chinese mitten crab, zebra mussels and Asiatic clam, all of which pose a threat to Britain’s indigenous river life like swan mussels and the river limpet. The team will also be on a special lookout for the endangered depressed river mussel (Pseudanodonta complanata) and European eel (Anguilla anguilla) hiding under rocks once the shore is exposed.

ZSL Conservation Ecologist, Dr Renata Kowalik, explains: “This is a rare chance to assess the spread of invasive species in the Thames. The Asiatic clam is certainly one of the most widespread invasive species and, along with the alien zebra mussel, is wiping out our native species by competing for food and space. Until we know exactly what’s going on under the surface, we can’t act to save Britain’s aquatic life, much of which is struggling for survival against stronger or more adaptable alien species.”

MCS Biodiversity Policy Officer, Dr Jean-Luc Solandt said: “The abundance of juvenile Chinese mitten crabs seen on the river bed at Richmond last year was astronomical. There is no other species that can compete with these crabs in British waterways, and they are spreading like wildfire. We need to better understand their numbers by recording them each year”

Jason Debney, Co-ordinator of the Thames Landscape Strategy added: “The River Thames is such a special place supporting a wide range of wildlife both in the water and along the riverbanks. The TLS is pioneering new ways to manage this unique habitat and is delighted to have teamed up with ZSL and the MCS to develop this important project.”

The Richmond draw-off happens each November and ZSL, TLS and MCS plan to return every year to gather more data. This will reveal trends and help conservationists to identify problems and threats quickly.

See more in our video below.