Thames Invasive Species

Thames invasive species monitoring Richmond

Aquatic invasive non-native species (INNS) are a serious problem across the globe and are considered by the IUCN to be the second biggest threat to biodiversity. The River Thames is particularly vulnerable to introductions of INNS due to the dense human population and high level of marine traffic, and is now one of the most heavily invaded river systems in the world. 

Since 2006, ZSL has been monitoring the invasive species in the Thames as part of a long term collaborative project. We want to know if any new species arrive in the river and how these new arrivals interact with the native species.

Richmond river bed survey

Every year in November, the weir at Richmond Lock is lifted to allow a portion of the river to drain naturally at low tide. We use this opportunity to scout the river bed for any species that are not native to this country's waterways. During the 2014 survey, the invasive quagga mussel (Dreissena rostiformis bugensis) was identified for the first time. This part of the river is home to populations of rare freshwater mussel, so it’s especially concerning that the quagga’s arrival will add to the pressures that threaten their future. Find out more about the discovery of Quagga mussels in the Thames.

Environmental DNA research

In partnership with Kingston University, ZSl is developing new methods to identify invasive non-native species by taken water samples and identifying environmental DNA (urine, scales, other biological material). This method will be a cost-effective way to monitor invasive species. 

London Invasive Species Initiative (LISI)

ZSL sits on the steering group of the London Invasive Species Initiative to identify key risks and management actions to reduce the impact of invasive non-native species to Londons wildlife.

Karen Harper, manager of the London Invasive Species Initiative, said: “You can help stop the spread of invasive non-native species like quagga mussel by following good biosecurity and applying Check, Clean, Dry every time you are out on our waterways. For quagga mussel this is especially important as the larvae are invisible to the naked eye, so you might not be able to see what you are transporting.”

Find out more about Check, Clean, Dry.


Quagga Mussel
The invasive quagga mussel was found in the Thames for the first time in 2014

Project information

Key species

  • Chinese mitten crab (Eriocheir sinensis)
  • Asian clam (Corbicula fluminea)
  • Zebra mussel (Dreissena polymorpha)
  • Quagga Mussel (Dreissena rostiformis bugensis)


PDF icon Report on ZSL's Freshwater Bivalve Survey in the Upper Tidal Thames (1.15 MB)

People involved

Joe Pecorelli, Anna Saltmarsh and Clara Obregon work on the Thames Invasive Species project. 

Partners and sponsors

  • Kingston University
  • Marine Conservation Society
  • Thames Landscape Strategy