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:
Our Fish Migration Roadmap officer started to walk London’s rivers to map all existing barriers. See the dedicated website to stay up to date.
Read the project report October 2019.
Main barrier data: Environmental Agency, Catchment Based Approach, River Obstacles app, Zoological Society of London, AMBER project, Canals & Rivers Trust and Essex Wildlife Trust
Additional barrier data: Amenity Water Management, Crane Valley Partnership, London Wildlife Trust (Lower Colne Fish Passage assessment) and South East Rivers Trust
Habitat data: CaBA
London boroughs and opportunity areas: London Datastore
Operational catchments and flood zone: Environmental Agency
World Heritage Sites, Heritage at Risk and Monuments data: Historic England
Waterways shapefile: in-house drawn (available on our Data Hub)
For more information about this exciting project, please contact the Project Officer.
Project is being founded by the Environmental Agency and the European Maritime & Fisheries Fund