Volunteers from Spelthorne Natural History Society are monitoring upstream eel migration on the River Ash for a third year in 2016. The Zoological Society of London has an eel trap on the Ash near Staines.  Here young eels travelling up the river are captured and measured by volunteers before being released unharmed to continue their journey. 

 The Ash eel monitoring station one of twelve which ZSL operates on the Thames and its tributaries near London.  It is also their most westerly monitoring station - and the one which is farthest from the sea.   Eels spawn in the western Atlantic Ocean and their young are carried east by the Gulf Stream to enter British rivers as small elvers.   So the very youngest eels tend to be those found closest to the Thames Estuary.

Results from the River Ash fit this general pattern well.   So far all the eels captured here have grown past the elver stage.  All have been young yellow eels with lengths between 180 and 350 mm.  Growth rates vary, so the length of an eel is only a rough guide to its age.  Nonetheless estimates suggest that these eels have typically been in fresh water for two to four years before reaching the upper end of the Ash.   The study has confirmed the presence of a small but thriving eel stock on the Ash.   Another good reason to continue removing barriers to fish movement along the river.

Further details from...

ZSL - https://www.zsl.org/citizen-scientists-help-save-the-european-eel

Spelthorne Natural History Society - http://www.snhs.org.uk



Design by LTD Design Consultants and build by Garganey Consulting. From an original concept by the Herts and Middlesex Wildlife Trust.