Environment Agency Fishery Officers stocked rivers and lakes in the West Thames region last week with over 5,000 young fish from their own Calverton Fish Farm. The introductions included barbel, chub and dace into the Rivers Thames, Cherwell, Wey, Loddon and Chalvey Ditch and tench to lakes in Surrey and Berkshire.
The operations were carried out in collaboration with angling clubs and fishery owners. In some cases the stockings were part of post pollution recovery plans such as the Chalvey Ditch near Slough, which has suffered a number of incidents in recent years with both Thames Water and DS Holdings Ltd fined for environmental breaches. The most serious instance included a near total wipe out of all life in the stream back in September 2009 when DS Holdings Ltd, trading as Envirogreen, released 4,500 litres of hazardous detergent-based chemicals into the waterway.
A biological survey after the incident revealed that the release of detergents into the ditch had a major impact on both the fish and macro invertebrate population for two kilometres, with nearly 100 per cent mortality of all groups. Four kilometres downstream of where the pollution occurred one third of the freshwater shrimp and about one quarter of the mayfly that inhabit the area had also died.
The recent stockings were not all in response to environmental trauma though and the addition of some 250 barbel, 250 chub and 250 dace into the River Loddon at Arborfield Mill was part of a wider River Loddon restoration scheme.
All of the stocked fish were marked on the belly using Alcian Blue dye which enables the Environment Agency to monitor their growth and movement at a recently completed Loddon fish pass and spawning channel.
Alcian Blue dye injected subcutaneously with a Panjet can persist for several years and anglers should look out for the distinctive blue spots on the underside of any fish they catch in future seasons and report weight, length and location data to the Thames West Area Office at Wallingford on 0370 8506506.
