Small water reservoirs (retainyjne, meliorative).
Water reservoirs are the most fertile among stagnant waters, although their productivity depends on the planned formation of fish stocks and – partly – from the use of appropriate intensification measures. They differ from carp ponds only in this respect, that the use of the reservoir is primarily based on the needs of water management, therefore, the fish management in these reservoirs can satisfy practically only the needs of fishermen.
The decisive factor for the angling use of these tanks is proper stocking, with particular emphasis on the species and age composition of the fish.. You should remember this, that we are basically dealing with production carp ponds, in which it is possible to achieve the desired quantitative increase by restocking. The main fish kept in these reservoirs is carp, but as a rule together with other suitable species, because only in this way is it possible to use natural food. Perfectly complemented by carp tench, to whom we should create more development opportunities in the tanks than has today. This fish, perfectly complementary to carp, it should create at least in these types of waters 1/5 fish stock masses. The rope has good breeding properties and is eagerly caught by anglers. So it definitely deserves closer attention.
Most of the small retention reservoirs feed the water of some stream and are almost the rule, that in a relatively short time, populations of various white fish develop in the tank. Typical are e.g.. roach, rudd, crucian, and more recently the silver crucian carp, which can proliferate in any environment. All these fish are zoobenthos consumers - white fish are therefore very serious competition for carp and tench. For this reason, this problem is worth looking at from different points of view.
From the productivity stand, however, without taking into account the quality of production, the most varied and numerous fish stocks are desirable and can only be guaranteed, that all natural food resources will be used up. If we were willing to catch crucian and roach as eagerly as carp and tench (maybe we would finally appreciate these fish) the presence of other white fish in the tank would be desirable. We, however, have “higher”: for us fish is only carp. Roach will remain a fish weed for a long time, so the economic point of view must recede in this case, and the problem remains open. Therefore, the only way out of this situation is in stocking with predators, from which to expect, that they will eliminate white fish and prevent them from overgrowing. When we take into account the relatively high food needs of predators (is accepted, that for them the food factor is roughly 4-6 Kg), this solution will turn out to be very uneconomical and, whether we like it or not, we must treat it as a necessary evil or an emergency exit. Even if that's how fish stocks (and therefore the effects of fishing) the tank will qualitatively improve, it is still a waste to consider such a significant loss of production in the form of fish meat. It is true that it is the loss of white fish, but the meat is wholesome. It is therefore necessary to look for a solution that would effectively and satisfactorily get out of this vicious circle. The above facts appear in a more positive light when converted into monetary values, because the production of meat from predators is relatively profitable. A certain value of these fish is also their large dimensions, This allows the presence of predators in reservoirs to be assessed a bit more indulgently.
The rearing of predators in tanks used by anglers may in some cases have even more negative effects than those described above.. In tanks, which must for some reason remain full for several years must come to this, that the predator cast gets out of control – both by this, that some of the predators will reach high (undesirable in this case) size, as well as the possibility of these fish multiplying too much. The first possibility is more dangerous because the larger specimens of predatory fish, especially pike and catfish can even endanger the basic fish stock of the tank. None of the predatory fish mince in their food, it does not distinguish between more valuable and less valuable fish, in fact larger individuals (pikes or catfish) Whether they like it or not, they have to direct their attention towards the carp, and restocking with this species is a unique opportunity for them.
Among predators, we give priority to pike, the holder of many desirable traits. He is the most consistent liquidator of the fish 'weed”, anglers also appreciate it. However, we may get out of hand, and then, if it becomes too large, it becomes the terror of even larger carp fry. Pike grows extremely fast under favorable food conditions. It is in the reservoirs that three-year-old pikes can reach over 5 Kg. And these are dangerous predators. We do not want to discourage stocking with pike in the reservoirs visited by anglers, however, it should be done with caution and not at any cost. Caution must be exercised especially with tanks, where there will be no fishing for a long time. It is therefore debatable, sometimes used, the practice of protecting pike in reservoirs during the first years. The final effect of these actions is expressed in fishing 8-10 kilogram pike z 20-30 ha of reservoirs is only seemingly beautiful, in fact, it is a testimony to waste. In the case of a tank, which, depending on the situation, can be completely emptied and caught, the described risk does not take place.
Another of the group of predatory fish – sum – can be properly characterized like a pike, there are even chances of some individuals reaching considerable weight (in the long term), but the risk of carps being eaten by the grown catfish is even greater. However, in reservoirs caught by anglers, catfish can be recommended as a fish, which diversifies the fish stock and is an attraction for anglers, and otherwise very well (and more versatile than a pike) uses food.
The situation with zander is very clear. If, in the first two cases, we advised caution, In the case of zander, it is possible to recommend fish with it at least to any suitable reservoir. It is a fish perfect for this type of water. It is indeed considered a predator, in fact, however, it would have to be characterized as an omnivore, because apart from small fish, it can even eat plankton and benthos (and is content with these), hence, it makes the best use of natural food resources among predatory fish. Feature, which cannot be overestimated is this, that spawning can take place in almost any tank, also cares for the offspring, and thanks to this, the outlays related to stocking with it are much lower than in the case of colonization with pike or catfish. A further economic benefit is to be seen in this, that zander – due to its limited possibilities – it can only get smaller fish. Thanks to this, only the fish weed is really eliminated, there is no risk at all, that he would feel like a carp. Therefore, when creating a fish stock with pike perch, you can safely allow small carps to be introduced into the tank, thus remaining in harmony with the elementary principles of economics.
Only complaint, that can be put forward for a zander comes down to this, that its gains are relatively small compared to pike. Although this disadvantage is objective, we can partially compensate for it with the earlier stocking of zander, and in particular by varying the age originally introduced fry. If these recommendations are followed, you can start fishing for zander in 3-4 a year after stocking. Compared to pike, it is admittedly a later date, but we will be rewarded for it in the future, because we will have an attractive and easy to get fish.
Many factors affect the productivity of a tank, depending on them, the efficiency is on average in the range from 100 into 300 kg per hectare. Larger and, as a rule, deep reservoirs are less efficient than the shallower and small ones. The production of the tanks, however, is not stable, but it changes significantly over time. It is the largest in the first 4-5 years after refilling. It is mainly due to this, that there was an abundance of organic matter at their bottom (then we should fish more intensively). The process of losing value by tanks can be eliminated by various measures, np. summer and wintering (periodic discharge of water), liming and biological methods.
