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Berlin Environmental Atlas

02.08 Fish Fauna (Edition 2004)

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Streams

This category covers 11 bodies of water in Berlin, including the upper Spree, small tributaries of the Havel and Spree, and the tributaries of the large lakes. All still show at least rudimentarily the near-natural habitat structures characteristic for streams, such as pools, meanders, back currents, turbulences, and various bottom sediments. Particularly overflow areas, coarse-grained sediment and meanders, all near-natural structural elements, have been removed almost everywhere by hydrological construction measures. This has led to a major elimination of those stream-dwellers which were tied to these structures. The strict protection of still-existing stream habitats as well as the restoration of some of those destroyed would constitute a very valuable contribution to fish-species protection. Other streams have changed markedly in their character, and have been heavily polluted by the discharges of sewage treatment plants. They are described under the category sewage-treatment plant discharge channels.

The Fredersdorf Mill stream arises northeast of Berlin on the Barnim plateau, and has a catchment area of about 230 sq.km. After flowing through Kessel, Fänger and Bötz lakes, it starts its actual 27.6 km long course, which leads to Müggel Lake. The last 3 km or so are within Berlin, in the borough of Köpenick. The Rahnsdorf weir, on Berlin territory, stops any migration of fish from Müggel Lake. Moreover, the biotic association in the Fredersdorf stream above the dam facility is extremely anthropogenically impaired by drinking water discharge. Since Well Gallery B of the Friedrichshagen waterworks was brought into operation in 1983, large stretches regularly fall dry during the summer, which is the reason for the above-mentioned survival pit in the Rahnsdorf basin. Currently, 16 species of fish have been verified in the Fredersdorf Mill stream, including Habitat-Directive species such as the weatherfish, but ever less frequently. Since the Fredersdorf Mill stream was reported as a protected area under "Natura 2000", this population development of Habitat-Directive species is extremely alarming. Without the year-round water supply already demanded in 1993, and the elimination of the existing obstacles to fish migration, the stocks in the stream can hardly sustain themselves in the long run.

The Western Drainage Trench branches off from the weir of the Spandau citadel trench and empties into the Havel below the Spandau sluice. Immediately below the weir, there is a relatively strong flow, and the sediment is sandy to gravelly. Here, lotic (flow-loving) species of fish find suitable habitats; chub and dace have been verified. Further downstream, in areas with a lower flow, the bed is muddy. The shores seem near-natural, and are tree-lined almost on their entire length. A total of 16 species of fish have been verified. The Western Drainage Trench is undoubtedly an important spawning area for the fish of the Havel, particularly for the lotic species.

Canals

Canals are artificial waterways with monotonous, reinforced shores (ripraps, concrete or steel bung walls), largely constant breadth and depth as well as a mostly trapezoidal profile. Berlin has more than 100 km of canals, if the canal-like structures of the Spree River in the inner city areas are included. Fish make only seasonal visits or migrations, because of the lack of structures important for fish, such as spawning, shelter and feed areas. The number of fish species present is thus dependent on the fauna of still bodies of water with which they are connected. As a comparative analysis of the fish population of 27 waterways of the northeastern German lowlands has confirmed, the typical federal waterway cenosis shows nine characteristic and nine typical associate species of fish (Wolter & Vilcinskas 2000). Thus, the good ecological potential of a canal according to the EC-WFD would lead one to expect the presence of 18 typical fish species. Currently, an average of only 12 species are verified in the Berlin canals.

The Gosen Canal, completed in 1936, is today managed for fisheries by the DAV, and connects Dämeritz Lake and Seddin Lake. Its shores consist largely of ripraps. Its mean depth is 3 m, its width 35 m; aquatic plants are very rare in the canal, shore reinforcement measures as well as the breaking of the waves caused by navigation are the necessary reason for that. Currently, 16 species of fish are verified in the Gosen Canal.

The canals in the city center, such as the Landwehr Canal and the Kupfergraben, have been developed even more monotonously. For reasons of space, the shores are perpendicular here, and are solidly sealed. Thus, unlike the ripraps of other canals, they are not even usable as spawning substrata by hard-substrate spawners like the perch or the ruffe. A total of 23 species of fish were verified in the canals; the canal with the largest number of species was the Teltow Canal, the southern connection between the Spree and the Havel, which showed 19 fish species.

Trenches, Melioration Trenches

This category consists of small, hardly structured, largely straight artificial streams. They were mainly built as inflow and outflow trenches for the sewage farms, but also for drainage, e.g. of the Gosen meadows in Köpenick. Their profile is trapezoidal or rectangular. While the outflow channels of the sewage farms are heavily contaminated by nutrients and pollutants, the pure melioration trenches, i.e. the irrigation or drainage trenches, are typically only polluted if their surrounding countryside is or was intensively agriculturally used. The abandonment of sewage dissemination and the drop of the ground-water table caused many of the trenches in the north of Berlin (the former Buch sewage farms) to dry out.

The Great Sprint Trench is a strongly weed-clogged melioration trench connected with the Lübars pond. Both species of stickleback were verified in it. With regard to ichthyologic value and protection, it should be treated as equivalent to the sewage-farm trenches (see below). Maintenance measures may be necessary to prevent the overgrowth and hence the disappearance of this trench.

The feeding of mechanically cleaned Havel water made the re-settlement of submersed makrophytes such as featherfoil, starwort, and water yarrow possible in the Kuhlake. The plant stocks, very thick in some places, support the growth of rudd and pike. The source of the Lietzen Trench is west of the village of Schönow, near Bernau in Brandenburg.

The Lietzen Trench drains the sewage farms at Hobrechtsfelde, flows to the west past the Bogen Lakes, and into the Panke at the Karow ponds. Besides the two stickleback species, crucian and gibel carp were verified.

The Prisen trench which is extremely monotonous and straight, largely drains parts of the Hobrechtsfeld sewage farms into the Lietzen Trench. Makrophytes and other structural elements are completely lacking. Within the last few years, the trench frequently dried out, which is why no fish were verified.

There are many discharge trenches around the discontinued Buch sewage farms, remainders of 100 years of such use. They are today dry during the summer because of the lowering of the groundwater table. Both stickleback species were found in almost all sewage farm trenches. They are the species most adapted to this kind of extreme biotope and find their last refuge areas here. Since the remained small trenches have been preserved, the populations of sticklebacks has during the last few years stabilized at a level which is low in comparison with the habitat supply prior to the extensive groundwater lowering, for which reason the endangerment level of both species has been reduced in the current Red Data Book (Wolter et al. 2003). Little trenches are typically only settled by two or three fish species. This number can, however, increase considerably if the trenches are connected with rivers or lakes and are used as spawning and breeding areas by the species inhabiting the latter. Thus e.g. 12 species of fish from the above-mentioned Riemeisterfenn and Grunewald lakes regularly migrate to the connected Fenn Trench.

Sewage-Treatment-Plant Discharge Channels

To safely discharge the considerable volumes of cleaned sewage emitted every day from the major Berlin sewage-treatment plants, small creeks were improved to increase their drainage capacity, redirected (Panke), straightened, clear out and reinforced with ripraps or concrete plates. Examples are the Panke, the Wuhle and the Neuenhagen mill stream. In the course of this development, monotonous, fish-hostile gutters whose water is considerably contaminated with waste heat, nitrates and various salts were created.

The "Silent Don" is an approx. 5-meter wide additional runoff channel for sewage peaks of the North Sewage-Treatment Plant in Schönerlinde. Its cross-section is trapezoidal, its shores are reinforced with stone packets. No fish have been verified in ten years. The reason, in addition to the lack of migration possibilities from the surrounding bodies of water, is also temporary sewage waves. The degree of organic burden is not preclusive of fish settlement.

To the north of the Heinersdorf ponds, the North Trench branches off from the Panke, flows through the north of Berlin and empties into Tegel Lake. Its artificial bank reinforcement, its straight course and its structural poverty makes this body of water appear very non-natural. Only three thorny sticklebacks were verified, although the North Trench is theoretically accessible to other fish species as well (e.g. from the Steinberg Lake). Probably, temporary strongly salt-contaminated sewage waves limit fish settlement in this body of water as well. Three-spined sticklebacks, of which anadromous populations also exist in coastal areas, tolerate higher salt content than other freshwater fish species.

From its source south of the city of Bernau, the Panke flows through the north of Berlin to empty into the Spree. The original mouth and the entire stream course in the borough of Mitte have been piped since 1987, and have fallen dry for at least 15 years. Even in the rest of the river's course, nothing recalls the time when the only certain verifications of occurrences of trout, creek lamprey and loach in bodies of water now part of Berlin were found here. In the past, a popular destination for outings, only the spring areas and the section flowing through the Pankow Public Park recall the original stream today.

The Wuhle flows through the boroughs of Hellersdorf and Marzahn at the edge of the city, to flow into the Spree at Köpenick. The body of water today marked on road maps as the Wuhle flows parallel to the original "Urwuhle," and is a fully developed drainage channel with a trapezoidal profile, partly graveled, partly sealed in concrete. The Wuhle is used for fishing from the retention basin in Biesdorf to its mouth into the Spree. During the last few years, it has shown thick, extensive sub-aquatic plant formations, with Kammlaichkraut, predominating. The Wuhle is divided by the Wuhle basin into two different ichthyologic sections by dam facilities which cannot be overcome by fish. Fish migration is possible from the Spree into the lower portion, so that 15 species, which also represent the species spectrum of the Spree, were verified here. Since 1993, the number of fish species in the Wuhle above the basin has dropped to 8. At present, the future development of the Wuhle and its fish population is not foreseeable, since the watercourse and draining conditions will change fundamentally, due to the above-mentioned closing of the Falkenberg sewage-treatment plant.

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