The Environment Agency (EA) conduct regular monitoring of fish stocks in the River Blackwater, with one recent survey of Hawley Meadows shown in their video clip below.
They use a technique called ‘depletion surveys’ as part of the National Monitoring Programme. This monitoring is in accordance the Water Framework Directive (WFD) sampling programme. Which is a piece of European Union legislation designed to preserve, restore and improve the water environment. It establishes a framework for managing the water environment in a holistic manner taking into account environmental, social and economic factors.
A fixed transect of river is netted at either end then the fish stunned, retrieved, measured, then released unharmed back into the river. This technique is very effective at establishing the health and size of individual fish, the biodiversity or range of species, as well as the fish density and total biomass for the transect.
This monitoring is useful to measure the success of conservation work we have carried out to increase the range of habitats in the river. Working with the EA, Wild Trout Trust and our volunteers, we’ve secured large woody debris and hawthorn brash in the river, and created riffles and gravel beds. By altering the channel dynamics, quiet spots are developed for sheltering fish, whilst faster flow scours off overlying silt exposing gravel beds for spawning. This EA monitoring demonstrated that following our river improvements, the density of fish increased 4-fold in 2012 to 0.9 fish/m2.