Our website uses cookies so that we can provide a better service. Continue to use the site as normal if you're happy with this, or find out how to manage cookies.

Main Biodiversity Resources in the Tidal Thames - Species


Bird count

The principal source of information on numbers, distribution and trends in wetland birds is the Wetland Bird Survey (WeBS), which (in different forms and under different titles) has been running since 1947 and is jointly administered by the British Trust for Ornithology, the RSPB and the Joint Nature Conservation Committee, with the Wilfowl and Wetlands Trust being associate members of the partnership.

Most of the Thames Estuary, but not the upper river, is covered annually by these coordinated monthly counts of wetland birds, undertaken within defined sectors or count units. The counts are undertaken approximately 2 hours either side of high water, and represent the best available estimates of the numbers of birds using the site.  There are 24 regularly counted units within the PLA’s area of jurisdiction, which are set out below.

WeBS Count units within PLA jurisdiction (Thames Estuary)
  1. Benfleet Creek
  2. Canvey Point
  3. Cliffe Creek and Offshore
  4. Cliffe and Cooling Offshore
  5. Cliffe and Cooling Marshes
  6. Coombe Bay Offshore
  7. Dartford to Littlebrook
  8. Easthaven Creek
  9. Higham Bight
  10. Leigh Marsh and Two Tree Island
  11. Lower Hope Point Offshore
  12. North Grain Offshore
  13. QE11 Bridge (Dartford) to Swanscombe
  14. Redham Mead
  15. Shorne Marshes Offshore
  16. Southend Seafront
  17. St Mary’s Marsh Offshore
  18. Thameside
  19. Tilbury to Mucking
  20. Vange and Holehaven Creek
  21. Wakering Stairs
  22. Yantlett Beach
  23. Yantlett Saltmarsh and Creek
  24. Yantlett and Allhallows Offshore

Data for the five year period 2002/03 - 2006/07 have been analysed to identify patterns in species distribution and relative importance for bird use of different parts of the estuary. This is presented on maps illustrating the relative importance for the principal bird species of the various parts of the estuary. The maps illustrate the relative density of bird use of the WeBS count sectors during the autumn, winter and spring seasons. It must be borne in mind that these counts represent bird use during a period of approximately two hours either side of high water, and birds may be differently distributed at other states of the tide (see below under Birds at Low Tide). More detailed information on bird numbers and distribution is set out in Appendix 1

High tide bird data will be fully updated at the five year review of the Conservation Management Framework in May 2014.

 Birds at Low Tide

In addition to the so-called Core Counts carried out around high tide, the Wetland Bird Survey includes periodic counts taken around low water, which give a better picture of the distribution of feeding birds in intertidal habitats. The WeBS partnership aims to arrange a low tide count on most major estuaries on a six year cycle.

Unfortunately, the last systematic low tide counts available for the Thames were carried out in the winter of 2002/2003 and are thus not of recent provenance. Furthermore, they were undertaken only along the south side of the Thames between Shorne and Grain, and therefore present only a partial picture of usage across the estuary as a whole.

For these reasons, no attempt has been made to present these data visually. The counts are available here (tables).

Once more recent data becomes available, an analysis of this information will add significantly to knowledge of bird distribution at low water.

Other bird survey data

A significant amount of bird survey work has been undertaken in connection with the proposed London Gateway port development on the north side of the Thames at Shellhaven. These have focused on Holehaven Creek, the foreshore immediately adjoining the refinery site, and North Mucking Flats to the west of the development site. Most recently, intertidal bird survey work was commissioned by the port developers DP World and carried out between September 2007 and May 2008. Earlier work, commissioned by the PLA, was undertaken in broadly the same area (but with some geographic variance) during the winters 1999-2000 to 2002-2003; and adjoining the refinery site, commissioned by BP Oil UK Ltd, during January-March 2005. These surveys confirmed the importance of the study area, notably the role of Holehaven Creek for black-tailed godwits and Mucking Flats for avocets (regularly supporting nationally, and in some winters internationally, important numbers of these species).

In addition, wintering shorebirds were surveyed in the vicinity of Oyster Creek, Canvey Island between October 2005 and March 2006, in connection with proposals for dredging work to improve access to moorings. Relatively high numbers of five species were recorded but none exceeding nationally or internationally important levels.


  • Darren Frost/Cambridge Ecology 2008. North Mucking Flats and London Gateway Foreshore Intertidal Estuary Bird Survey September 2007-May 2008
  • Philip Shaw/Ecological and Landscape Services Shellhaven Refinery and Mucking Flats Shorebird Survey November 1999-March 2000
  • As above September 2000
  • As above October 2000-March 2001
  • Philip Shaw/Ecological and Landscape Services London Gateway Shorebird Survey October 2001-March 2002
  • As above October 2002-March 2005
  • Philip Shaw/Ecological and Landscape Services Mucking Flats Wintering Shorebird ‘Sensitivity’ Study 2003
  • Philip Shaw/Ecological and Landscape Services Wintering Shorebird Survey at BP Refinery, Coryton January-March 2005
  • Philip Shaw/Ecological and Landscape Services Oyster Creek Wintering Shorebird Survey 2005-06


The Thames is an important freshwater and marine fishery and plays an important role in providing a nursery for juvenile fish. 125 species had been recorded in the tidal Thames up to the end of 2010. 

The fish population of the Thames has been studied since the 1950s by Alwyn Wheeler at the Natural History Museum using data from power station intakes. Regular survey work has been carried out by the Environment Agency between Richmond and Mucking since the early 1990s. CEFAS regularly surveys the outer estuary for bass and herring, and the Zoological Society of London monitors the creeks for small migratory eels.

Survey work carried out by Marine Ecological Surveys Ltd in 2001-02, 2004-05 and 2007 (see references below) showed a relatively low biomass of fish in the outer estuary compared with the mid and inner estuary, although the inner estuary has a lower species assemblage diversity. Most species surveyed showed considerable seasonal and inter-annual variability. Information on fish populations has been incorporated into the documents comprising the consultation on future flood risk management in the Thames – Thames Estuary 2100.

In commercial terms the Dover sole is of special significance in the middle and outer estuary. Smelt are caught for the fishing bait trade, and eels are also caught by a thriving fyke net fishery below Tower bridge.

Although a number of species of high conservation importance (including Sea Lamprey, Smelt and Shad) have been recorded in the tidal Thames over the years, the absence of established spawning populations of such species (notably those listed in Annexes II and IV of the EU Habitats Directive) means that there is no statutory driver requiring specific actions in relation to fish. The European eel has recently been reported to have declined and is now listed by the IUCN as critically endangered. England has eel management plans for each River Basin District that detail all aims and targets for the improvement of the population and recruitment in English waters. The Thames eel mangement plan can be found at the Defra website here.

References and resources:

  • Environment Agency website State of the Environment  
  • CEFAS website 
  • IUCN website 
  • Thames Estuary Partnership website (opens in a new window)
  • Marine Ecological Surveys Limited 2002. Seasonal Changes in Fish & Epibenthos of the Lower Thames Estuary
  • Marine Ecological Surveys Limited 2006 and 2008. Spatial & Seasonal Changes in the Fish & Epibenthos of the Lower Thames Estuary
  • ABP Marine Environmental Research 2007. Benthic Ecology of the Thames Estuary

Marine mammals

The main recent source of information on marine mammal presence in the Thames is the Thames Marine Mammals Sightings Survey coordinated by the Zoological Society of London (ZSL), and conducted between July 2004–June 2007.  This brought together sightings reported by a range of river users and members of the public, from the tidal limit at Teddington and a line between Shoeburyness and Sheerness. During the period in question there were 340 sightings of 691 mammals, made up as follows:

Bottlenose dolphin


Harbour porpoise


Common seal


Grey seal


Unidentified seal species




In addition, white-beaked dolphins are believed to be present in the outer estuary, although none were recorded during this survey.

There are no breeding sites for seals within the PLA area of jurisdiction. It is likely that dolphins and porpoises breed in the outer estuary.

All marine mammals in UK waters are afforded protection under the Wildlife and Countryside Act 1981. The four species identified during the survey are all listed in Annex II of the EU Habitats Directive and as such are species for which Member States are required to consider the establishment of Special Areas of Conservation (SACs) although no such SACs have been established for these species in the Thames. They are also listed in Annex IV of the Directive, which names “Animal and Plant Species of Community Interest in Need of Strict Protection”.  This prohibits the deliberate capture, killing or disturbance of the species, and the keeping, sale or exchange thereof except under strictly limited and licensed situations.

It is anticipated that adherence to the PLA’s suite of environmental policies and practices, and the recommendations and actions set out in this Conservation Management Framework, will afford an appropriate level of protection to marine mammals in the context of the PLA’s operational activity. On going records are continuing to be collected by ZSL in the Marine Mammal Survey.


  • Kowalik, R., Pryor, A., Causon, P., Shaw, A. 2008 Thames Marine Mammal Sightings Survey July 2004 – June 2007 ZSL 


The London Bat Group and Thames Landscape Strategy have carried out surveys of the upper tidal Thames and sites alongside the river banks such as Barnes Wetland Centre. The PLA considers the impact on bats of works on the authorities sites.


A number of studies have been undertaken on aspects of the distribution of marine invertebrates in the Thames Estuary (see references below), although taken together these do not amount to a comprehensive understanding of the distribution of these organisms. None of the species recorded within these datasets are individually identified within the citations of international or national environmental designations. Nor are any species identified in either the UK or local Biodiversity Action Plans with the exception of the reef-forming polychaete worm Sabellaria spinulosa, which appears to have a patchy distribution with the highest abundances in the outer estuary around the Kentish Flats, the northern part of the approaches and off Canvey Island.

There is accordingly an absence of statutory drivers connected with invertebrates that would require location-specific actions to be taken, over and above general good environmental practice.

Data on invertebrates are presented in documents comprising the consultation on future flood risk management – Thames Estuary 2100.


  • EMU, 2005a.Thames Benthic Study Winter Survey. A report commissioned for the PLA.
  • EMU, 2005b. Thames Benthic Study Winter Survey. A report commissioned for the PLA.
  • ABP Marine Environmental Research, 2007. Benthic Ecology of the Thames Estuary (and references included therein)

Return to CMF Index

Proceed to Biodiversity Impacts