Fish expert’s theory on Colnemere deaths
ANGLER’S MAIL magazine has been reporting on the wipeout at hush-hush lake Colnemere, where casualties included prized carp, The Black Mirror.
Angler’s Mail has heard various theories and our magazine report covers what happened, with fish deaths being investigated including huge bream and tench.
Fish health scientist and former EA fish health officer Ian Wellby, whose company, BlueRoof, advises clients.
He told www.anglersmail.co.uk: ‘In the event of an algal die-off, the supply of oxygen through photosynthesis is dramatically reduced, and the demand for oxygen is increased by the bacteria that quickly colonise and break down the dead algae.
‘This situation can be made worse by decreased direct diffusion of oxygen during the atmospheric conditions of a summer storm.
‘Another possibility is that the thermocline was disturbed. During summer the warm water rises to the top of a lake and the cold water sinks. These two layers separate at a distinct point known as the thermocline.
‘Below this point the cold water becomes devoid of oxygen. During a storm with lots of cold rain and high winds the mixing of the water can disrupt the thermocline, which then allows the top and bottom layers to mix, resulting in a rapid and dramatic decline in the oxygen levels,’ Ian told www.anglersmail.co.uk
- Read full Colnemere coverage, along with more on Two Tone and carnage at Thamesmead in Angler’s Mail magazine (issue date August 31).