To understand Turnover we need to understand a little about the water and temperature ranges.
Armed with this invaluable information finding winter feeding fish becomes a precise matter rather than trial and error.
Being cold bloodedcreatures by nature in water that is particularly cold lethargy takes over fish stocks which in turn induces sluggishness and slow reactions.
Too hot and fish simply seek the comfort of more compatible depths with temperatures that are more suitable to their natural body requirements.
Within this band of temperate water fish will happily feed.
Different species are often found at varying depths in the 'Comfort Zone'.
Lochs,lakes and tarns have a layer of warm water over a layer of cold water sandwiched in between these layers is a narrow band of water known as thethermocline – this is the feeding zone.

TURNOVER– AN EXPLANATION.

In the coldest winter winds severe temperature drops occur within the upper layer,when those temperatures drop to 4 degrees centigrade and below the thermocline breaks down.
The upper warmer layer now at it's densest and cooling fast simply 'sinks' to thebottom of the loch displacing the cold water column.Which now risesto the surface.
This action which occurs at least once a year presents otherwise 'stale water' to the natural elements to be well oxygenated and inhabited by the resident wildlife and fish populations.
Thus Mother Nature's way of natural regeneration of the water comes into play.
Shallow lochs only reaching depths of about 15 feet do not develop a thermocline but are often heavily weeded blocking out the sun's rays,natures alternative.
Detritus and other rotting vegetable matter dead leaves and weed tend to gather in the bottom ten feet of the loch.Eating away at oxygen levels as the decay gets under way.
Particles of detritus can sometimes been seen in the water accompanied with an aroma of rotten eggs.
A sure sign that the loch has ' Turned Over ' it can be fatal to fish stocks suffering from deprived oxygen.
This is the exception rather than the norm and not to be confused with the same
' symptoms ' during the heat of the summer.

WHAT DOES THIS MEAN TO THE FISHERMAN

During the period ofchange as the thermocline dissipates and warm and cold waters displace each other pike will access the deeper water which is for the time being well oxygenated and carrying prey fish too.
Under normal circumstances this level would be avoided due to oxygen depravation.
For most fish this is a temporary measure,oxygen levels soon build back up,a thermocline is re-established and as late January early February approaches pike are already migrating into the shallow margins pre-spawning.

In effect if during mid to late winter fishing in the shallows does not produce the goods and little if any activity is evident,cast that little bit further into deeper water that most anglers would avoid.
There is a very good chance that feeding fish may found here.

John