The waters of the Stołowe Mountains supply drainage areas of two seas. The streams: Pasterski Potok, Czermnica and Darnkowski Potok run to the North Sea, and Pośna, Cedron, Kamienny Potok and Red Water (Czerwona Woda) to the Baltic Sea. The mountain streams featuring big gradients, good oxygenation of water and its low temperature offer most favourable conditions for trout. Apart from the trout, some other interesting species can be found, such as the common loach, greyling and bull-heads. The morphology of trout proves its adaptation to the environment of mountain streams. A muscular, slightly flattened body and regular fin arrangement denote a perfect swimmer that can cope with rapid stream currents. Its big eyes add to the profile of efficient predator hunting in daylight. With the speckled pattern of colours, trout are blended into the environment of shallow waters with stones and gravel. Hence, the sides of adult fish bodies maintain numerous dark and red spots, the latter usually light-edged. Mountain streams are food-deficient environments, however the trout are not demanding about their food. They feed on crustaceans and case- worms found on the bottom of streams, and also on insects, frogs and even tiny mammals. They are particularly good at catching insects, for which they can even jump above the surface of water. Fishes found in mountain streams are not closely-related, and come from distant geographical regions. Bull-heads are a good example. They represent fauna of sea origin. Their features seem to be unique, as compared to trout for example. These include: lack of air bladder, lack of scale, and their abdominal fins are shifted far to the front. Two species of bull- head are found in the Stołowe Mountains, namely the Miller's thumb, in the streams of the North Sea basin, and Cottus poecilopus. The Stołowe Mountains stand of the latter is the farthest to the west in our country and it is found in the streams of the Baltic Sea basin. The head of this fish is large, slightly flattened and equipped with a wide mouth opening. Due to the lack of air bladder, bull-heads are constantly in contact with the bed, and do not have to struggle with the current. It is sufficient that they cling to the bed. It is very difficult to spot the bull-head when it is not moving. It can get covered up with sand while lying on the bed. In spring, the bull-heads start to build their nests. The zale-fish using its well- developed pectoral fins digs the cavity under a stone, then attracts the female-fish, which immediately stick the spawn to the stone from underneath. Now, the role of female-fish is ended and the male takes the role of a nest keeper. Swaying its pectoral fins, it oxygenates water, and guards the nest until the offspring becomes self-dependent. The bull-heads feed only on invertebrates. They prey on gammarids, insect larva, snails and other waterbed invertebrates. The loach, the next in turn inhabitant of streams, that can be found in lower parts of the Stołowe Mountains is of completely different origin than the bull-heads. It belongs to the carp family and originates from warm climatic zones of the South-eastern Asia. The loach is a small fish, just as the bull-heads averaging between ten and twenty centimetres. Further similarities with the bull-heads include their model of life (nocturnal life, feeding on waterbed invertebrates) and shape of head. Unlike the bull-heads however, they have more elongated and flexible body and short regularly arranged fins. Such a shape makes them easy to get under stones and into bank cracks where they search for a hiding place against strong currents of the mountain streams. Their skin which is only party covered with scale produces large quantities of mucus. They feed on very tiny animals which they catch with the use of three pairs of barbels fixed to the upper lip and mouth corners. In the streams of lower parts of the Stołowe Mountains, which are slower and wider, the species of grayling are found as well as the brook minnow, which is a protected species.
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