|Joe Pecorelli thanks all volunteers for their work this season|
ZSL project lead, Joe Pecorelli, said the summer of 2013 had been good for the European eel, commenting the increased elver numbers at our Hogsmill trap since habitat improvement works at the Clattern bridge in August was a particularly encouraging sign.
This Citizen Science project is providing otherwise unavailable data to conservation organisations which enables prioritisation of investment in conservation measures, he said. Without volunteers like ours from KU and local residents getting their waders on and spreading the word, the plight this species is facing would only be known to a limited few. This kind of project works wonders for raising the profile of 'uncuddly' species like the European eel and wider conservation issues such as river habitat quality.
The programme has expanded from 3 sites in 2011 to 11 sites in 2013 all monitored by volunteer teams, and provides a valuable insight into the migration of the European eel in the Thames catchment. Joe explained that now is a good time to pause and reflect on the findings, with particular analysis of zero and low count sites. A review of active monitoring sites will be conducted and new ones at the River Ash, Teddington Lock and River Mole will be added to the scheme. With such intriguingly low numbers, monitoring at the Hogsmill trap will continue at Middle Mill, with a view to increasing check sites upstream as habitat improvement work is undertaken.
|Joe spreads the love for eels!|
- Merton Abbey Mills for the finest excuse for having to stop monitoring as a moorhen took up residence nesting on the trap!
- River Crane for a victory for hope over experience as the team have never seen an eel in the three years they have been involved!
- Bow Locks for the most enthusiastic email circulated to all volunteers upon discovering an eel in their trap!
Following Joe's upbeat roundup and emphatic thanks to all eel monitoring volunteers, the Environment Agency's Darryl Clifton-Dey spoke about installing eel passes to overcome barriers on rivers, and Andy Thomas from the Wild Trout Trust described the importance of good quality habitat in urban rivers.
|Darryl illustrated the common problem with eel passes fitted onto gauging weirs.|
Darryl emphasised that not all weirs need to be removed straight away to improve things, just critical sites downstream which will enhance habitat access for the eels. He listed the numerous barriers to migration including gauging weirs, flood gates and culverts which are all hard for eels to navigate, especially as eels are not good swimmers (despite their ability to swim the 2000miles from the Sargasso sea strangely!).
The European eel (Anguilla anguilla) prefers to crawl in damp conditions, rather than battle against a strong flow. It needs to be able to find the entrance to an eel pass easily and it must exit into suitable low-flow habitat too. Darryl commented that although eel passes are increasingly being installed, not all are working due to a lack of understanding of these basic needs. Fixing a pass to a gauging weir for example, is tricky as the Environment Agency needs to ensure unobstructed passage of flow over the sharp metal plate in order to measure river flow. A pass must have a trickle of flow for it to allow eel movement, but also mustn't inhibit the edge of the weir and skew calculations. That said, Darryl claimed research has proven that eel tiles can be bolted on in some cases with minimal interference with the gauging weir calculations.
|Andy Thomas highlighted the advantage of volunteer work parties to improve river habitat|
He underlined the benefits of using large woody debris (large tree sections) in rivers to create pools, shelter and act as fly egg-laying stations. Coarse woody debris (brash) too can encourage sediment accumulation, serve as a natural flow deflector and again provide shelter for fish from predators. Management of trees and vegetation on the riverbanks can also play an important role by affecting the amount of light reaching various sections of the river. Coppicing, for example, must be maintained on a cyclical regime to ensure the benefits of more light are also maintained.
After a tasty lunch and networking opportunity, ZSL staff kindly gave a tour of the seahorse breeding facility at the Zoo, as a thank you to all volunteers.
|Excited eel monitoring volunteers enter the Aquarium for a sneaky-peak behind the scenes!|
|A poor swimmer against currents, the Seahorse clings on to vegetation in its tank|