Way back in 1968, when I first started getting serious about carp fishing, I was given an excellent piece of advice by a long time carp angler who told me, “it’s better to have one bait in the right place than a thousand baits in the wrong one.” That’s is very sound advice and I have never forgotten it. At first sight it sounds like an obvious statement to make but go deeper and you’ll see that there are wider implications here and correct bait application is without doubt one of the contributing factors to success.
Let's look at some typical angling situations that we face in our day-to-day carp fishing on reservoirs and lakes (rivers are a different proposition). Carp waters exist in all shapes and sizes but I guess it is fair to say that they can be divided roughly into two types; deep reservoirs formed behind a dam at the foot of a valley, and shallow flooded areas of plains, farmland and forest. The huge expanse of this lake typifies a reservoir that is formed when the dam is built across a wide area, holding back water over many hundreds of hectares. Such a reservoir will be very expansive, like an inland sea. This is Raduta Lake in Romania.
Huge though the reservoir is, that shouldn't mean it would necessarily be hard to fish, as this beautiful photo of a thirty pound common from Raduta shows. It’s all too easy to be complacent about your fishing when you set out on a typical holiday session. A little voice whispers in your head that you’ve got a week (or more) to build up a swim and as your bait is the best there is it is only a matter of time before you start hauling! I wish it were that easy! Sadly, I have watched confidence drain away as blank day follows blank day, and often the cause of the blank is nothing more than poor swim choice and/or badly positioned bait within the swim.
Large natural lakes and artificial reservoirs come in all shapes and sizes but one of the most common types of lake is formed where a dam is constructed at the foot of a valley, holding back the flow of a river or stream until the lake forms behind the dam. There are invariably three common features to all this type of lake; the river bed, the steep valley slopes and a fairly narrow strip of shallows formed by less steeply sloping bank at the waters edge. The riverbed will be situated at the foot of the flooded valley and like most rivers the area will be surrounded by trees. These may or may not be cut down to stumps prior to flooding, but either way they are natural havens for carp and their food. Rising up from the riverbed you will find the sides of the valley climbing steeply upwards. Finally the steep slopes level off a bit and the angle in the margins becomes less acute. 
Naturally there will be exceptions to this rule! I defy anyone to classify the underwater contours of Rainbow Lake! It is like an egg box as it is littered with features both above and below the surface. Application and positioning of your bait carpet and hookbait is absolutely vital. 
We need to examine the subject of light penetration and how this affects your fishing. When you stand by the lake it will appear to be blue or grey but this is simply caused by reflected light. The lake water in reality will probably either be a green colour due to the millions of tiny plants suspended in it, or brown because it contains sediment or has picked up pigment from the soil. In fact the one characteristic of lake water is that it is more or less transparent. Light penetrates the surface and passes down into the lake where it provides energy for plants to make their own food by the process of photosynthesis. Plants are the basic food material, either directly or indirectly, of every living thing in the lake, so the profusion or otherwise of plant life is a vital factor in the lake’s productivity and they are the key to a lake’s entire ecosystem. The strength and direction of the wind plays an important part on the turbidity. Here a strong wind pushes up waves that stir up the lakebed causing the margins to become heavily coloured ad the lakebed is disturbed. The coloured lake water carries lots of natural food that has been disturbed by the wave action. Find the food: Find the carp! 
When light enters the water the energy it provides is dissipated by the waters turbidity and by the depth of the water. Plants can only photosynthesise in the most well lit areas of the lake. In gin clear lakes they may grow at depths of up to 20m, but in more cloudy water they may not be able to grow in water below a few meters deep. Plant growth determines the richness of a particular area of the lake and where weed growth is most vibrant that is where food production will be at its highest. It follows that carp, which rely on the plants and the food harboured therein, will patrol the shallower areas of the lake in preference to the deepest areas of the lake. 
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However, that’s not to say that they will not also move into deeper water at certain times of the day, and as we have already discussed, in clear waters the productive area could extend down to as deep are 20m. It figures therefore that if you can find areas of natural weed growth you should have a fair chance of pulling some carp into the swim by adding your bait to the natural food larder provided by the weed. Don’t be sacred of deep water but always bear in mind that a lake’s productive area may be limited to shallower areas due to the turbidity of the lake water and the associated light penetration it permits. In fact, on many deep-water lakes and reservoirs the productive area might amount to less than 10% of the overall surface acreage. This photo shows a typical gravel pit in eastern France. The depths in these kinds of pit vary greatly and you can actually find deep water right under your rod tips. In fact, I found that the margins were very productive for me. 
Stratification of the lake water starts when it warms up with the arrival of spring, and it gets into full swing with the heat of the summer. Hot days with no wind causes a rapid increase in the temperature of the surface water, which, being less dense than the colder water in the depths, will float on the top. Gradually a situation arises where there is a marked difference between the surface water and the water lower down. The narrow separation zone between the two layers is called the thermocline, and it is here that the water temperature changes abruptly. It must be remembered that it is not the temperature itself that causes the stratification but the difference in the densities of the two temperature layers. Long-term stratification is not beneficial to a lake and some mixing of the two zones is desirable. However, only wind action is capable of mixing the layers and deep lakes may remain stratified for long periods. Shallower lakes experience more effective mixing, and undergo seasonal cycles of mixing and stratification, the major factor in their productivity. If wind action is a significant factor in your day-to-day carp fishing, the lake of it can severely hamper it! 
…On the other hand…! 
The other type of reservoir is one that is formed when the dam (or dams) is built across a much wider area, holding back water over many hundreds of hectares. It is likely to be much shallower and expansive. The slope of its banks, both above and below the surface will more gentle in profile. Significant underwater features will once again be the ancient riverbed, large, mainly flat areas of cut off tree stumps, and huge expanses of mud. In such a lake the water depth is not such a significant factor in determining the lake’s productivity. 
In the 1980s I fished a highly productive lake that was formed by damming a river and allowing the lake to form over a shallow plain. The dam was built over a hundred years ago and a large area of former farmland was flooded. Now many years later those once lush green fields have turned into mud and silt, formed by the laying down of particles of sediment. These particles are, a) inorganic silt and b) the organic remains of plants and animals. As is the case in all lakes of this type, the balance between a) and b) determines the organic content of the mud, and it's value as a food larder for bottom feeding species like carp. 
The shallow nature of the lake allows maximum light penetration and weed growth and the silt is a rich soup of organic matter. Wave action created long narrow bars of tiny stones and gravel and these run the length of the reservoir along the direction of the prevailing wind. The gravel is also important as it plays host to other types of natural foods. Low water reveals the position and shape of these bars. 
In the few years the lake was open as a fishery the carp thrived in the lake, growing from juveniles of about 0.5kg to over 18kg in weight. Unfortunately it is no longer open as a carp fishery but at the time it was one of the best carp waters in the UK. In 1998 the lake was drained and all the carp were transferred another reservoir not far away. This one is deeper; more steeply sided and is far less productive in natural food production. As a result the fish have not thrived in their new home. This example shows you the importance of natural food held not only in the weed growth but also in the mud and on the gravel. 
Lac de la Poiteviniere (Chateau Lake) is a well-established estate lake. It features a large shallow plain where the river enters and the lakebed then gradually falls away to the deeper parts of the lake that follow the course of the old river. At it’s deepest point near the outlet the lake is no more that four meters in depth while the large area of shallows is less than a meter deep. The lake is hard bottomed for the most part and consequently little weed grows. There is a small area of pads in the northwest corner of the main part of the lake and that’s it. With the lake being more or less flat for much of its bed, there are few actual features to attract and hold fish and as a rule you make an area hot simply by the frequent and generous application of bait. 
I found the lake to be one of the hardest to read, as it gives no hint of its underwater plainness. Often the only thing that moves the fish around is angler pressure or a strong wind. Mind you, on such apparently featureless lakebeds even the slightest hump, dip, gully or even a few stones constitutes a feature so you should try to take the trouble to find as many of them as you can. Any little drop-off or shelf that deviates from the normal pattern of the lakebed should be investigated. 
Just to give you an example of how important even the tiniest feature in an otherwise featureless bowl can be, let me tell you about a session we had in 2001 on just such a lake in the south of France. After arriving late on a Saturday evening we spent the last few hours of daylight wandering around the lake looking and listening for fish. Neither seeing nor hearing anything we went out in the boat early the next morning and tried to find something worth fishing with the echo sounder. Nothing significant showed up and we came to the conclusion that the lakebed was almost entirely devoid of features. It wasn’t until we were heading back to the boat slip that the sounder registered the tiniest of deviations in the flat profile of the lakebed. It had risen no more than a few centimeters but it was worth investigating further. I reversed direction, motoring back along the course of the boat’s wake, and up came the feature again. I dropped a marker float on it then set about expanding the search around the marker to get a better picture of the little hump. Once I was confident that I could find it again I took landmarks then lifted the marker out. 
Suffice it to say that the tiny feature became very significant as the trip went on, and we caught some very big carp off it. By using the echo sounder’s Grey Line facility we could see that it was rock hard with no silt or mud on top of it. However, the surrounding area was much softer and there was quite a bit of silky-soft weed growing up a few centimeters. In total I suppose the hard area was the size of a decent dining table, and that’s exactly what it actually was. The carp would visit this little feature regularly throughout the day and polish it clean of food and weed thus forming a typical dinner table. 
Some of the carp in that lake were gorgeous beyond words. This fabulous 'zip' linear I shall cherish to my dying day! 
So there we have it. As my learned friend told me way back in the day, don't waste your bait. A single hookbait in the right place is better than a thousand baits in the wrong one.
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