Recent articles and discussions on watercraft prompted me to look a little more at my own fishing (as all good articles and discussions should) which resulted in me looking into and composing this article. To begin with what is a Thermocline? A quick look at the ‘Collins Concise Dictionary’ tells us: a thermocline is a “temperature gradient in a thermally stratified body of water, such as a lake”. Put simply, it is a layer of water situated between two other layers of water – these are known as the ‘epilimnion’ and the ‘hypolimnion’. During the warmer months, as we all know, the water at the surface is heated by the sun and the surface temperature warms up considerably (epilimnion). This actually ‘floats’ over the colder water below (hypolimnion). Now between the two you have a layer of water that forms which is called the thermocline. Before we go any further, this is not meant to be a technical article, but I think we need to understand the basics about that which I am about to waffle on about! I will therefore, keep it as simple as possible, I am after all, a very simple person myself! (No comments thank you!). I think it is safe to say that most carpers who frequent FISHINGmagic practise their art on stillwaters much like myself, with perhaps just the odd foray onto the rivers and canals. The impending onset of winter fishing, and the thought of fish location, has got me thinking about water temperature throughout the varying depths of the stillwaters I fish during the colder months. Find the fish Of course, fish are cold-blooded creatures, therefore their bodies will always be the same temperature as the water around them. But water temperature actually has a significant influence upon the activities of all fish. During the winter months, colder water slows down their metabolism – for instance, they only need about a quarter of the food they would munch through in the summer. As a consequence of this it becomes even more important to find where the fish are – or at least where they are likely to be.
As winter approaches, frosts and cold winds lower the temperature of the upper layers. As the warmer water rises, this in turn cools until the water in the upper layers begin to stabilise at around 37 to 39 degrees Fahrenheit. At this point the water no longer mixes but ‘layers’ begin to form (please refer to the techy bit above). The water divides into not only different levels of temperature, but varying densities. At 39.2 degrees Fahrenheit water is at its densest, and fish become extremely lethargic. So, generally speaking, we could expect the warmest part of any lake to be at the bottom. However, it is not quite as simple as that. This only really applies to much deeper waters. In shallow waters the colder surface or upper layers will tend to reach the bottom – the thermocline is thus eliminated, consequently in shallow waters the temperature fluctuates a great deal. In deeper waters the thermocline remains all year round, more so in the warmer months which is why the ‘zig-rig’ can be so successful. Further to the above, another factor that must be taken into consideration is that of wind. A brisk wind will mix and aerate the different layers to a greater or lesser degree depending on the depth of the lake and the severity of the wind and its duration. As a result in the winter the warmer part can often be found, not only towards the bottom, but also to one side of the lake – the ‘leeward’ side.
So how does all this affect one’s fishing? Shallower lakes, because of their smaller volume of water, will tend to be more temperamental, and one’s fishing will depend very much on weather changes and the resultant fluctuating temperatures. Accordingly, in the colder months, a few hours sunshine will warm the water a little and may well trigger the carp into a feeding response. But what of the deeper waters? Let us remember that fish are really no different than other ‘animals’, in that there is a kind of ‘comfort region’ within which they would wish to exist. What I mean by this is that fish will thrive more in the warmer layers of the water during the colder months, therefore it makes sense as an angler to target these warmer layers if possible in the hope of catching one. I remember either being told or I read somewhere years ago that ‘90% of the fish are in 10% of the lake’, and I believe this especially runs true during the colder months. It therefore becomes very important to find the thermocline. But again, it is not that simple! I mentioned previously the different densities. Often in winter a slight fluctuation in the temperature, and thus the density of the water, will result in fish awakening from their lethargy and thus begin to feed. Bearing this in mind, when planning where to fish at your chosen lake, it is worth considering also the ambient temperature as well as the water temperature itself. Obviously, if it is a relatively warm day, and has been so for say two or three days, it makes sense that the water temperature will rise, and, accordingly, the thermocline will alter. What was once the warmest part of any lake may no longer house the majority of the carp you are targeting. Such a change may well induce the lake’s residents to come further up in the water. So, have you considered using the zig-rig for winter fishing?
Another point worthy of consideration is that during some winters it is very cold indeed, and if this is the case then the colder layers of water will reach the very bottom of the lake – even on very deep lakes! Different levels of oxygen will be present or not as the case may be, and this scenario brings in other considerations, because as the lower density water drops to these depths the fish will then often move from the bottom to shallower water where any sunlight will gently warm the surface layers and to where there is potentially more food in the water. These are all relevant points and so it really is important to take all things into consideration when planning where to fish. It is equally as important to ensure one has a suitable variety of rigs for any given situation that different levels or density of water can present. In other words, it is no good trying to present a bottom bait to carp that are happier in a layer of water that is, for example, 5 feet from the bottom! So be prepared to take the time to experiment and find the fish. There is a device on the market, basically a thermometer, which can be cast into the lake, and which will take on a sample of water from where it momentarily rests prior to retrieval. This is a good way of finding the layer at which you want to present your bait! After using your marker float set-up to find a suitable area to fish you can either present a popped-up bait to the required depth, or, find a depth of water equivalent to the depth of the thermocline, ie, where the thermocline hits the bottom, and present your baits accordingly. This article is designed to be thought-provoking and to perhaps encourage others to think a little more about their winter carp fishing. So, in conclusion, when planning your session, as well as looking for signs of fish activity and fish-holding areas – consider the temperature of the water, the ambient temperature, and once you have plumbed around and found the depth of your chosen swim, then find the layer of water at which the fish are likely to be situated and fish for them accordingly. |
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