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Posted: Thursday 17th December 2015 by Living Rivers


Fish are a group that are often overlooked when it comes to conservation and eels certainly aren’t a species that most people think about. But the European eel (Anguilla anguilla) is a species we should all be paying attention to. The plight of the eel is often unknown outside of the fisheries community, but over the past three decades stocks have declined 95% landing it a spot as critically endangered on the IUCN Red List (to put that in perspective, water vole populations have had a perceived decline of 90%).

The European eel has a complex and mysterious life cycle which takes them from their freshwater habitats in the rivers of Europe and North Africa to the Sargasso Sea where adult silver eels are believed to spawn. Living in freshwater and spawning at sea is a process known as Catadromy and eels are one of the few species to do this (The opposite of this is Anadromy, think salmon!). After hatching in the Sargasso Sea, larval eels then ride the Gulf Stream back to the freshwater rivers of Europe and North Africa transforming into glass eels as they go. Upon reaching estuarine waters such as the Thames, glass eels become elvers, moving upstream into freshwater systems like the River Lea they undertake another transformation into yellow eels, eels then remain in freshwater for a number of years. Little is known about the transformation of eels and even less is known about what cues them to make the final transformation to the silver eel where they again undertake the long journey back to their spawning ground in the Sargasso Sea.

Eel stock declines have been suggested to be caused by habitat loss, barriers to migration, parasites, pollution, over-fishing and climate change. There are currently 2392 barriers to eel migration in the Thames river basin, which includes the River Lea and its tributaries. Recognising the plight of the European eel, the Lea Catchment Partnership decided to make them a priority species for which a separate action group was formed. The action group secured £28,500 of funding from the Catchment Partnership Action Fund to address at least two of the barriers facing eels on the River Lea.

Lea Valley Regional Park Grand Weir

Holyfield Weir and Grand Weir (above) in the Lea Valley Regional Park were identified as the best barriers to hit first. Allowing European eels to pass these structures will give them access to vital habitat at Cheshunt Gravel Pits. Agreeing this with the Environment Agency, Living Rivers is now working with a local engineering and steel fabrication company to come up with some designs for structures that can be fitted to the weirs, allowing eels to move upstream without compromising the flood defence function of the structures. If our designs meet with the approval of the Environment Agencies flood defence team, we hope to push forward with manufacture and installation soon into the New Year, allowing eels access to Cheshunt by early spring.

Riverfly Day 2016

Following the success of the Riverfly Day in February held on the River Chess, the Herts & Chilterns Riverfly Hub decided to run another Riverfly Day in 2016. This time Riverfly Day will be held in Hertfordshire on the River Lea in Lemsford. The day is an opportunity to learn more about the world of Riverflies through a morning of talks ranging from Riverfly photography to the ecology of Hertfordshires Plecoptera, followed by an afternoon field trip to the River Lea at HMWT’s Lemsford Springs nature reserve, featured in this year’s Springwatch. Spaces are limited and likely to fill up fast so best to book online early.

Other News

As many of you will be aware, in October I was able to attend the CPRE Herts’ ‘Rural Living’ awards at which the Riverfly Hub was the overall winner in the Environment category. So a huge thanks from myself to all those involved. The night was a double success with HMWT going on to win an award for the Reedbeds for Bitterns project at Amwell Nature Reserve.

It was Sustainable St Albans week 21st - 28th November, so I ventured to Aboyne School with the Living Rivers Chalk Stream in a Tank to talk to Y4&5 about our important chalk streams. The tank is left from the Save Water Save Wildlife Project, an exciting project with schools piloted in 2013. The project fits in well with the Y5 curriculum and has a real focus on local rivers and issues, hopefully funding will be found to run this project again.

The Living Landscape Champions went out for their Christmas walk and lunch. A Trip up around the Ash Valley near Much Hadham followed by a meal in The Bull. A big thank you to them and all the other Living Rivers and Riverfly Partnership volunteers for their hard work this year.

Read Living Rivers's latest blog entries.


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