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Forgotten Landscape Project: Identifying the barriers to eel migration

BART are investigating the migratory passage of European eels in the Lower Severn Vales as part of the Forgotten Landscape Project. We are aiming to assess the success of eel passability into the project area by looking at where eel passage is detrimentally affected by the presence of barriers and establishing the priority barriers for more detailed fish passage investigations.

The Severn Estuary

The European eel (A.anguilla) has recently been classified as ‘critically endangered’ on the IUCN red list after populations have declined by 90-95% since the 1970s (IUCN, 2014). This decline is in spite of their extensive ecological and socio-economic importance, with approximately 25,000 people generating income from eel fisheries and aquaculture in Europe alone during the 1990s (Moriarty & Dekker 1997). Multiple factors have contributed to the decline including the exploitation and trade of glass, yellow and silver eels, habitat loss, pollutants, parasites, disease and predation. Once in freshwater, hydraulic schemes constitute a physical barrier to free upstream and lateral migration and, unless alterations for passage are considered, limit the areas where eels are present, as well as their densities.

European eels have a fascinating life history that sees them migrate from the Sargasso Sea near Bermuda to European freshwaters and back again. They begin their lives on the far side of the Atlantic as eggs and drift towards Europe with the Gulf Stream, hatching into leaf-shaped larvae as they travel. When they arrive in Europe they transform into the transparent fish known as glass eels, taking on the recognisable cylindrical shape before making their way into freshwater through estuaries and rivers. Having completed 7,000 kilometres of their migration, eels darken in colour and become known as elvers and attempt to migrate upstream where they can remain for more than 20 years. During this time the “yellow eels” will feed on invertebrates and fish until they are ready to reproduce and migrate back to the sea as silver eels to spawn. It has been noted that larger eels are more effective swimmers and better suited to traversing barriers such as weirs and dams in both directions so their ability to find food and suitable habitat on UK rivers is crucial for their spawning success.

It is important to recognise the physical barriers to eel passage because they must be able to swim upstream to feed and grow for a significant part of their lives before they are able to make the long journey back to their spawning grounds. There are many natural and human-made structures that can prevent eels (and other fish) from migrating. These include: tidal gates, dams, weirs, barrages and sluice gates. Eels and elvers are robust creatures and are able to travel along damp surfaces to reach a water course, however the barriers are often too steep, the water too fast flowing or surface too smooth for them to negotiate. This initial research will identify the presence of these barriers and establish the priority barriers for more detailed fish passage investigations and the available options to enable more successful eel migration (downstream and upstream) in the Severn Vale.

Tidal gate: an immediate barrier to eel migration

Thank you to Charlfield Angling Club

BART are very grateful to Charfield Angling Association member Hans Thomsen, who, when fishing became too difficult for him, kindly donated his fishing kit to help raise funds for the rivers that provided him with years of sport. This thoughtfulness is really appreciated and needed as our rivers are under tremendous pressure. Hans generosity raised over £1500 shared between BART & The Wild Trout Trust.

Charfield Angling Association also showed their own support for our work by adding their annual donation towards our work – thanks and thanks too for looking after the lovely Little Avon in South Gloucestershire.

The Little Avon

Spawn to be Wild – the big releases!

11 primary schools across Bristol, South Gloucestershire, Bath and Somerset have been out in local rivers releasing 550 young European eels which they have been studying as part of our Spawn to be Wild project. Each primary school looked after approximately 50 elvers (young eels) for 4 weeks, during which time they learnt all about eel life cycles, the river habitat and threats to eel survival.

The eels were bought from UK Glass Eels after being caught by elver fisherman on the River Severn, after which the eels took a quick detour in each primary school.

The eels spend between 10-70 years in the headwaters of rivers, in small tributaries, ditches and streams before they make the epic 5000km migration back to where they were born in the Sargasso Sea to spawn. All elvers were successfully released in a series of lovely events in rivers local to schools. The children were certainly sad to see them go but have promised to go to their local river and try to spot their elvers in the coming years!

The children were able to hold an elver and let it go
Wick Primary with their trophy and certificate after a successful release event
Oldbury on Severn pupils released their elvers into the Oldbury Naite on a lovely sunny afternoon
Pupils from Christ Church Primary, Clifton, released their elvers into Bristol harbour

The Spawn to be Wild project is an incredibly important project to raise awareness of the European eel. These eels are critically endangered and their long and complicated life cycle means that only a very small percentage of them survive to adulthood. They are an important part of our river ecosystem but with so many barriers to their survival, mainly from human influences, they are now at risk of extinction. The human stresses upon eel survival include climate change, overfishing, pollution, habitat loss and barriers to their migration caused by weirs and dams.

Did you know that the illegal trade of elvers is worth more than the ivory trade?

Through the environmental education delivered in this project the children have become much more aware of the wider world and how humans are having a detrimental impact upon it, which directly impacts the wildlife we find in our local areas. For far too many children outdoor play, especially in or near rivers, has become a thing of the past. In today’s urban society filled with technology many children do not spend time outdoors getting to know common wildlife species and enjoying seeing them in their natural habitats. By bringing wildlife into the classroom we hope that this will inspire the conservationists of the future, making children and their teachers, parents, friends and families more aware of the direct influence we are having on wildlife, and reconnecting them with nature.

A great school display on elver facts and stories

We are pleased to report that we have gone from initial answers to ‘What lives in your local river?’ of ‘sharks’, ‘jellyfish’ and ‘whales’ to types of freshwater invertebrates, aquatic birds and the mammals at the top of the food chain. We have had some brilliant eel questions, such as ‘how does pollution affect the eels senses? and ‘how will elvers get up rivers if we don’t get rid of weirs?’

An elver begins it’s life in the Newton Brook, Bath after being released by Farmborough Primary!

Thank you to Bristol Water, A Forgotten Landscape and the Avon Frome Partnership for funding the project this year and to the Sustainable Eel Group and UK Glass Eels for their support. Here’s to Spawn to be Wild 2020!

Understanding our rivers – BART school visits

Alongside our elver assemblies and check ups for our Spawn to be Wild project, BART have been busy running lessons in our 11 project primary schools.

We have had countless great questions about the elvers, however one in particular got us thinking, ‘Why does it matter if all the eels die?’. To answer this, BART set about running food chain lessons for Reception – Year 4 classes.

Firstly, the children split into groups of 6, where each child was asked to colour in one element of the aquatic food chain. By making these into hats, the children then became their part of the food chain! They were asked to organise themselves into the correct order and we had some great discussions about what eats what. The fastest group was then bought to the front of the class and we discussed what would happen to the rest of the creatures in the food chain if the eels were lost – cue some dramatic death drops to the floor, great acting everyone!

Our food chain hats!

BART have also bought in live river invertebrates and discussed water pollution and water saving during various lessons.

Thanks to everyone who is taking part in this project, we are looking forward to the releases next week!

Thanks to this year’s Spawn to be Wild supporters, Bristol Water, A Forgotten Landscape and the Avon Frome Partnership

Bristol Avon Waterblitz 2019

Bristol Avon Rivers Trust are excited to announce the 2019 Bristol Avon WaterBlitz; a yearly campaign to collect as many water quality samples as possible in a week from across the Bristol Avon Catchment, between Saturday 1st June – Friday 7th June.

Join hundreds of people in using the free and simple to use water testing kit to sample your chosen river or stream in the Bristol Avon catchment (Bristol, Bath, South Gloucestershire, Wiltshire and North East Somerset).

To register and take part, please follow the link below to sign up and you will then receive a free water quality sampling pack in the post. Sampling kits are limited so please register by Friday 24th May to ensure you can participate:


Thanks to Bristol Water and the Avon Frome Partnership for supporting this year’s Waterblitz!