The Technical Bit
Every now and again, when reading through the Angling Press, I read of anglers having results that have surprised them during the winter. Sometimes it is because they have had a lot of action from shallow water and sometimes its because they have caught a good fish from a lake that is half frozen. In any event, a lot of anglers still think that as a lake cools down the fish move into the deepest areas and stay there until the water warms up in the Spring. This is very seldom the case.
Water is at its maximum density at thirty nine point two degrees Fahrenheit and at this point the fish become extremely lethargic. Its points of minimum density are at thirty two degrees Fahrenheit and two hundred and twelve degrees Fahrenheit, so it can therefore be seen that a small drop in the temperature of the water reduces the density to a far greater degree than a small rise. A reduction in water density is what seems to trigger the carps feeding spells in the winter; carp actively feeding under newly frozen ice has often been witnessed and reported.
As Autumn approaches and surface temperatures start to drop the fish move into deeper water where it is still warm, as the temperature continues to drop so the fish move deeper and deeper until the surface temperature gets down to thirty nine point two degrees Fahrenheit (or four degrees Celsius for those of a metric mind). When this happens the surface layers drop through the other water and eventually end up in the deepest areas of the lake. Waters of different densities do not readily mix, so the lake will have several different densities of water stratified throughout its depth. These layers of water will mix very slowly and will be helped by any undertow present. As more dense water drops to the bottom of the lake, the temperature will remain constantly at thirty nine point two degrees Fahrenheit in the deepest areas for the entire winter.
Fish that have moved into deep areas will start to move back to shallower water as the denser water drops into these deep areas and will feed quite readily in temperatures as low as thirty three degrees Fahrenheit. Armed with a knowledge and understanding of these temperature gradients, the winter angler can score very heavily indeed when conditions are correctly interpreted.
I have seen several references recently to fish feeding in very cold shallow water being attributable to high oxygen levels, but, as the water in a lake holds its highest level of oxygen in the winter anyway, this is just nonsense.
A few years ago I fished two waters for a couple of winters and kept records of feeding times and corresponding temperatures. The first was a three acre mature pit with a fairly low stock density. The margins here are about ten feet deep and drop away to about twenty feet, twenty yards out. I found that most of the carp activity in the winter occurred in a twenty yard wide band that ran from the middle of the eastern bank to the middle of the western bank. The margins of this area were fished by Terry and myself throughout a winter and although we only had about a dozen takes between us, they all came on the coldest days and nights. Baits fished in the deeper water by ourselves and other anglers produced almost nothing. The most action we experienced came in early January when a cold snap caused the water temperature to drop suddenly. During the afternoon, Terry caught a low double and shortly after dark a twenty two pound mirror. A couple of hours later I caught a twenty four pound common, by midnight the lake had frozen, fish had been crashing out in front of us right up until the time the ice formed. Three days later the lake had started to unfreeze and, with ice still covering parts of the lake, we did another twenty-four hour session. I had a twenty-five and a half pound common at lunchtime and at midnight Terry had a thirty-one and a half pound common, he caught a twenty one pound mirror a couple of hours after this. All the takes had come from a depth of between six and ten feet, the maximum depth in this lake is about thirty feet.
The next day the temperature started to rise and the water in these margins eventually rose to forty one degrees Fahrenheit. No action was experienced by anyone on the lake until the end of the month when the temperature again plummeted. I then caught two more low twenties from the same area.
The other water I fished for a winter and kept records on was a shallow lake with a minimum depth of about four feet. It is about ten acres in extent and is fairly well stocked. By mid-December its temperature had dropped to forty degrees Fahrenheit and most of the carp had taken up residence in the reed beds at the eastern end of the lake, where they refused any baits that were cast to them. On the days that the water saw a small rise in temperature (as little as two degrees Fahrenheit), numbers of carp would move out into the lake and feed and several takes could be had between twelve noon and three p.m. by casting anywhere on their patrol route. Exactly the same action could be had between eleven p.m. and three a.m. on the nights when the temperature dropped by a few degrees. Rapid temperature drops could not be monitored due to the lake’s tendency to freeze.
Anyone who hasn't yet tried fishing in extremely cold conditions but would like to try should bear in mind the results that Greg and I had when fishing through two holes in the ice for a night. I caught two low doubles and Greg caught pneumonia, so keep it sensible.