CARP SCIENCE: Surface Foods for Carp

WORDS & IMAGES: Gareth Coombs Illustration: Laudette Sass

A most distinctive type of feeding behaviour occurs in carp when they feed on the surface. This kind of feeding behaviour can be very obvious as the fish make loud sucking noises while slowly moving just below the surface with their lips breaking above the surface film.

To achieve the sucking motion, the fish will briefly suspend below the surface and force water out of its mouth; the fish then lifts its head until the lips are either just below or slightly protruding above the surface and when it opens its mouth, water rushes in bringing food morsels with it. The principle is very much the same as when you are trying to fill a cooldrink bottle with water from a dam.

The exact cues that elicit surface feeding in carp can be obvious in some cases but quite mysterious in others. Carp very commonly feed on the surface when they are among reeds, beds of watergrass and beneath algae films. It is usually a slow feeding motion where they don’t spend a lot of energy and I have seen them nearly strand themselves on top of weedbeds as they manage to forcefully push nearly their entire body up onto the weedbed.

To understand what carp are feeding on when surface feeding one needs to analyse the ecology of the top water layer and how food organisms interact with it. In most cases, because carp feed on the surface among weedbeds and reed stands, one has to narrow it down to what is going on in the topwater layer within these vegetated areas. Water in well vegetated areas is typically moving very slowly and is well oxygenated (due to oxygen being released by photosynthesizing plants). The water temperature is also higher than deeper layers due to solar radiation. Oxygen released from plants makes the concentration of oxygen higher than if it were only dependent on the surface mixing and partial pressure. Warmer water, with lots of oxygen and sunlight stimulates biochemical processes, making it an ideal place for phytoplankton, algae and plants to grow.

That in turn, is again perfect habitat for water living insects as well as the nymphs of those insects that also graze on algae. Thus the top water layer in these planted areas is a nutrient rich soup of algae, diatoms, plankton, small insects and insect larvae. If you take a clear glass and scoop a small amount of water from these areas you will notice a cloud of suspended organic particles within it, and this is exactly what carp are going after. Furthermore, the top water layer is an area for other micro-organisms, particularly plankton and diatoms, both of these will also develop dense clouds (mostly invisible to the naked eye) just under the water surface. By slowly moving through this layer and sucking this water in, a carp is gradually extracting a lot of micro- food particles. As you can see, the top water layer can be amazingly productive as a source of natural foods for carp, which is one of the reasons why maintaining healthy bankside vegetation, reed stands and floating weedbeds is so important to sustaining a healthy carp population.

Fishing for surface feeding fish

To target surface feeding fish requires tactics that you would not associate with normal bank angling. Firstly you need to either float your bait on top of the surface, or suspend it in the surface film or just slightly below the surface. This cancels out the need for bite alarms and detectors but it does require a fair amount of concentration and typically you will only use one rod. When spotting surface feeding fish that are feeding close to the bank, an excellent strategy is to stalk up close to the fish and present a single, unweighted bait within 40cm of the fish. Carp are curious and will often quickly drop below the surface and head straight for the bait. If you are using a floating bait, watch the fish for a while and present the bait in the feeding path that the fish is following. Take great care however to first watch the area for a while and spot all fish that are in the vicinity as it is very easy to spook a fish that you overlooked by casting over it, and spoil the entire feeding event. Sight fishing in this way must rate as one of the most exciting ways to specifically target big fish and is every bit as exhilarating as casting to rising trout.

Managing aquatic vegetation

To promote healthy bankside vegetation is usually simple. Firstly, monitor the water quality to make sure that it is unpolluted – specifically there must not be an excess of nutrients such as phosphorous and nitrogen that cause algal blooms and eutrophication. Soil is another important feature, with healthy, organically rich soils being the best, however there is relatively little one can do about soil conditions unless you want to go about it manually which requires a lot of labour! Fortunately many types of water plants have relatively weak root systems and take up a lot of their nutrients directly from the water, so once again water quality is important. An extremely important feature of promoting water plant growth is the relief of the dam bottom. Water plants will invariably dominate in large shallow areas where they can root in the soil while floating on the surface. Thus if you are industrious enough to build your own dam, or want to alter an existing dam, make sure to create some shallows where the water is less than a metre deep and remains this depth for some distance into the dam.

The other side of the coin is what needs to be done when weed growth is too excessive. In such instances weeding can be very useful, particularly when weedbeds become too large, by removing them and aggressively cutting them back. This practice if also very important if you are planning on managing a day fishery, where clients expect to have several choices of area that they can fish. Using herbicides can also be employed, but do make sure they are specifically developed for the purpose and are non-toxic to other aquatic organisms.

Finally, we all like to release our fish, but if you want to maintain good aquatic vegetation, you must be prepared to cull carp either yourself by netting or heavy fishing. Managing a good fishery is much like managing a game farm. Large numbers of small fish will quickly erode your weedbeds and damage the root systems of young and emerging plants. The bottom structure of many of our dams consists of various mud and clay types that tends to make the water murky when too many fish are present. The old “rule of thumb” management principle still stands, namely remove as many small, juvenile fish as what you catch, but release all adult fish, in particular those heavier than 5kg.

The latest digital edition of THE BANK ANGLER / DIE OEWERHENGELAAR is now available!