Greater Thames Estuary Fish Migration Roadmap

Thames Estuary Partnership is working on an exciting new project that brings together – for the first time – all the data needed to improve fish migration routes and habitat in the greater Thames estuary. Our partners in this groundbreaking work are the Environment Agency, the Institute of Fisheries Management, the Zoological Society of London and Dutch consultancy Nature at Work

The impact of river fragmentation

In the UK we have fundamentally changed the way our rivers work, straightening and deepening their channels to get water off the land as quickly as possible. This has effectively turned them into water chutes, which benefited our agricultural and industrial industries by providing drainage and water transport corridors. We have also built weirs and sluices to control their flow.

But this fragmentation has led to some major problems. A river is meant to meander across the landscape and have areas either side that can flood safely, called floodplains. The meandering slows the waterflow, stopping flash floods and creating pockets of habitat for wildlife and plants. Floodplains allow for natural drainage and create wetlands that combat pollution and habitats for important migratory fish. The lack of these habitats, due to the presence of barriers, has contributed to the decline of these species. Diadromous fish, such as the European eel, bass, sea lamprey and flounder must be able to migrate between marine and freshwater habitats to reach their breeding, nursery and feeding grounds.

Various EU directives and national legislation require improvements to our rivers, and in turn, fish migration. Some great work has already been done to ‘re-meander’ rivers, restore wetlands and reconnect floodplains in the UK. And technical solutions to man-made barriers – collectively known as “fish passes” – are helping to recreate fishes’ natural migration routes. Although they vary in form and complexity, many enable fish to navigate barriers by swimming and leaping up a series of low steps leading into the water on the other side. 

Bringing together all the relevant data

We started out working at three different scales: the tidal Thames; the Thames river basin, and the marine plan area. This involved collaborating with partners across many administrative boundaries, such as London boroughs and county council areas. But of course, migrating fish do not heed human administrative boundaries. We soon realised that we need to work at more strategic level and analyse the barriers to migration across the entire estuary system, which has called for a more collaborative approach across multiple river basin districts and their coastlines. 

By bringing together and analysing all the relevant data on fish populations and migration barriers across the whole of the greater Thames estuary, we will be able to identify entire migration routes and create a road map of ‘major highways’, ‘A-roads’ and ‘B-roads’ that fish would use if there were no barriers preventing them. As well as helping to priorities where fish passes are needed, the completed road map will help to identify opportunities to restoring habitat during work on sea or flood defences, river restoration and land development. 

See the Greater Thames Estuary Fish Migration Roadmap in development below: 


Project feature: 

8th Annual IFM Specialist Conference – Fisheries Management in Estuarine and Coastal Waters

Talk of the Thames Spring/Summer edition 2018

IFM FISH 130. Summer 2018  


Data sources:

Barrier data: Environmental Agency, Catchment Based Approach, River Obstacles app, Zoological Society of London, Canals & Rivers Trust, Crane Valley Partnership and Essex Wildlife Trust

Habitat data: CaBA

Opportunity areas: London Datastore

Flood zone: Environmental Agency

Waterways shapefile: in-house drawn


For more information about this exciting project, please contact the Project Officer.