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A Fischweg (also fish moving assistance to be given in the vernacular frequently only fish stairs mentioned) is a water-structural device, which is installed in running waters, in order above all fish in the context of the fish migration the possibility obstacles (for instance pilot weirs or for overcoming.
All running waters organisms are dependent on the wandering through barness of waters. Fish moving assistance are thus arranged at moving obstacles in running waters. They make possible the overcoming of v.a. structural, artificial obstacles for fish and also small animals of the waters sole (macro zoo benthos).
The necessity for Fischwegen - so that legally and technically common term - is European-wide legally regulated among other things by the European Union water framework guideline.
To differentiate moving assistance for the fish ascent (fish ascent assistance and - lay close) are and for the fish descent (so-called ).
With the fish ascent one differentiates technical building methods nature near and. To the naturenear fish ascent assistance above all so-called raue ramps or raue sliding belong, also to resoling sliding and evasion-coagulate. Among the technical building methods for example slot passports and basin passports rank.
The fish descent represents so far finally a problem not solved yet in technical regard. At most hydroelectric power plants fish must pass the rakes and the turbines of hydroelectric power plants with waters downward the arranged migration. This is connected with a substantial mortality, whose height is dependent among other things on the type of turbine and on the size of the turbine. If fish on their moving way directed downward must wander through several hydroelectric power plants, complete loss of the fish is to be feared. This problem can be moderated with
With or fish stairs small Wasserbecken are built, by which the fish can overcome the difference in height between upper and underwater. Strongly artificially appearing, classical stairs like the accompanying illustrated, to Germany for the 1990er years are hardly still built and/or promoted from public funds. Since they offer ideal fodder places to birds with their flat Wasserbecken above all, they are a little effective. Besides they are hardly accepted often also after years and cannot to be helped to the moving fish thus not as desired.
A newer technology is the combination of fish ascent plant and boat lane, the fish Kanu passport.
Resole-slide are with naturenear stone latch plate installations manufactured basin structures, which make also with summer Niedrigwasser the migration for fish possible. Thus for example in the context of the project "Elblachs was replaced 2000 "in the Brandenburger Stepenitz system at the Schlatbach weir by a resole-slid, which overcomes a difference in height of scarcely two meters.
A game passport serves primarily to reduce the velocity of flow of the water. A Aalgang or a Aalleiter is a pipe, which is filled with gravel or brushwood.
With a fish elevator a large downward gradient can be overcome on small area. As also is the case for the other solutions, an artificially produced guidance current leads the fish to the desired place. They swim into a Wasserbecken that with a device escaping prevents. Regularly now the Wasserbecken is upward driven and dumped above carefully. Subsequently, the construction drives again downward and opens the inlet for the next fish.
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