Project status
Marine and Freshwater
UK and Europe
Contact details

The Tidal Thames, running from Teddington lock in the west of London, to the North Sea, is home to more than 100 fish species, many of which are commercially and ecologically important.

Species calling the Thames home include endangered species such as European eels, seabass, flounder, and smelt. The Thames is used as a nursery habitat, and a pathway between freshwater habitats and the open seas – making this area absolutely vital to the success of UK fish species and their conservation. 

However, like other estuarine habitats, this region remains poorly studied and there is a need to further our understanding of the ways in which fish are using the river in order to protect vulnerable populations from continued threats such as habitat loss, poor water quality and development activities.

A flounder being studied by ZSL conservationists

ZSL is working to conserve fish in the tidal Thames

Since 2015 ZSL has been studying fish in the tidal Thames with special focus on spawning grounds and the seasonal variations in juvenile fish presence and distribution. To date, we have conducted the most comprehensive studies of juvenile fish in any estuary in the UK, identified a previously unknown spawning habitat for smelt, an estuarine indicator species, and tagged the first fish to swim through central London. Through this work we have provided a benchmark to measure the health of fish populations over time. 

It is clear from our research the entire tidal Thames is essential to fish in their early life stages, from the central areas when they are just larvae and unable to swim, right to the extreme margins where the juveniles and adults rest and hide from the strong tides. 

ZSL conservationists and citizen scientist volunteers survey fish in the tidal Thames

To ensure that important life stages of fish species and their habitats are protected in the Tidal Thames, we have published a Guidance Document on Conservation of Tidal Thames fish through the Planning Process. This document provides a single point of reference to developers, planners, Biodiversity Officers and consultants on how fish should be considered when planning developments on or beside the river.

Learn more about our tidal Thames fish conservation 

Thames conservation

Our fish conservation project in the Tidal Thames is just one of the ways we’re working to conserve wildlife in the UK. 

  • Spurdog shark in the Thames
    Did you know, there are sharks in the Thames?

    The Greater Thames Shark Project

    Working together with anglers to better understand the importance of the Thames estuary to these animals and to ensure their long-term survival in the wild.  

  • Volunteers digging for invasive shellfish on the banks of the River Thames
    We're monitoring invasive non-native species in the Thames

    Thames Invasive Species

    At ZSL, we're working in the Thames to protect the wider ecosystem.

  • conservationists_wading_through_river
    A vital habitat for wildlife

    London’s Rivers

    Please help us health-check and survey our rivers as part of our ongoing programme of Citizen Science projects.

  • marine habitat
    Putting the health of our marine ecosystem first

    Marine Habitat Restoration

    Marine habitats are essential to the health of our marine ecosystem, and hold environmental and social importance, providing valuable ecosystem services.

  • a group of seals seen during our aerial surveys in the Greater Thames estuary.
    Protecting harbour and grey seal populations in the Thames

    Thames Marine Mammal Conservation

    ZSL has been monitoring marine mammals in the Tidal Thames since the early 2000s, to better understand and conserve species such as grey seals, harbour seals and porpoises.

  • Support our fight to protect the natural world