Country fishing association Brandenburg e.V. and institute for inland fisheries Potsdam-Sacrow - Stepenitz
|Contactpersons : Ulrich Thiel, Steffen Zahn||Topics : Reintroduction of salmon and seatrout, waterdevelpoment|
Impairments : Migration obstacles, watermaintanance, waterpollution
|Riverarea : Elbe
This report was provided by Ulrich Thiel :
The river Stepenitz springs near to the city of Meyenburg and flows into the river elbe after a length of 86,4 km at Wittenberge, at riverkilometer 455. The distance between the river mouth of the river Stepenitz to the estuary of the elbe is 272 km. The distance between the weir in Geesthacht to the mouth of the stepenitz ist 131 km. On its way from the spring to the mouth the hight difference is 84 meters. so for a lowland river it has quite a high incline of 1‰ . In the middel- and upper sections and in some of the tributaries the incline rises up to 5‰. In fact the rivers have sandy to rough gravel structures and at some places there are stony river beds. The watershed of the Stepenitz is 867,4 km2 and is with about 600 mm one of the most high-rainfall areas in Brandenburg. According to environmental authorities of Brandenburg the discharge at the river mouth is 1,5 m3/s (low-water), and von 6 m3/s (medium discharge) and 22,4 m3/s (maxium-discharge).
The system of the river Stepenitz has an outstanding meaning for protection of water and fishspecies because at the Stepenitz and at most of the tributaries there are large near-to-nature sections. Besides brooktrout and grayling there appear bullhead, minnow and brook lamprey. There exist some rest populations of the european crayfish and the freshwater pearl mussel. River lamprey come up frequent and sea lamprey swim up sporadic for spawning.
The river Stepenitz project was begun in 1997 as a joint venture between des institute of inland fisheries in Potsdam-Sacrow (IfB) and the country fishing association of Brandenburg e.V. (LAVB) . As a goal at the startup was stated that a self sustaining and for fisheries useable stock of salmon and seatrout should be built up aswell as free passable watersystem by the example of the river Stepenitz. At the same time the high symbolic grade and the sympathy of the salmon should be used for a broad protection of species within the aquatic surroundings. Stocking of salmon takes place since 1999 based on fieldmappings of the IfB . In the following two years there was breed stocked. From 2001 on yearlings were set out. The stocking is undertaken in near-to-nature section in several tributaries. One year old fishes are set out in the mainstream of the Stepenitz and its biggest tributries, the Doemnitz and the Kuemmernitz. During 1999 to 2007 there were about half a million salmon-fry, (mainly of the west-swedish Lagan-strain) and 133.000 older fishes mostly one year old, salmon of the strains Aetran (west-sweden) and Skjern Å (Denmark) , that were marked with an adipose cut (Skjern) or a cut of the right ventral fin (Ätran) . Besides that there were 340.000 ofseatrout breed being stocked in that time.
Beginning with 2002 there were yearly confirmations of returners. Until the end of 2007 a total of 231 mature migratory salmonids (109 salmon and 122 seatrout) were caught and registered with electro-fishing. Repeatedly there was the confirmation of natural reproduction of salmon proofed by genetic surveys. It is assumed that also seatrout are able to reproduce naturally. So far the biggest ever caught salmon (since the beginning of the project) in the Stepnitz was 98 cm and 8 kg of weight. The biggest seatrout weighed 5,5 kg measuring 77 cm.
In the year 2007 the rainy an cool summer obviously led to an increased run of migratory salmonids. Already in june there were salmon and seatrout in the mouth of the river havel of which some were caught in a control reuse that was installed for scientific purposes in the fishway of the weir in Gnevsdorf. In the Stepenitz the first catch of a seatrout of the year succeeded on the 28th of september. The first salmon was caught at the 12th of octobre with electro-fishing. During control-fishings until the end of december there were caught a total of 29 salmon and 44 seatrouts with a total weight of 204 kg, measured and set out in the headwater of the barrage of Perleberg. There has to be kept in mind in this context that only the part of the returners is counted that doesn't reach quick enough the vertical-slot fishladder at the weir of the mill. The other ones ascend over the fishway and are not registered.
So far there was no striping off of returners for artificial breeding because first of all we wanted to get informations about the migrations of the fishes within the riversystem. The main points of interest were what waterbodies and stretches are used for spawning and wether the fishes are able to find and pass the fishladders. For this purpose several times salmon and seatrouts were equiped with telemetic transmitters. Despite of the size of the watersystem and the small amount of spawners spawning beds of big salmonids were regularly found ; in single cases spawners were observed or detected near to spawning beds.
Free way of passage
The main route from the river mouth of the Stepenitz to Putlitz is passable on a stretch of 55 km for migrating fishes after the building of a rock ramp at the location of the Zellwolle weir in Wittenberge in august 2007. Also the linear passage of the main tributaries is so far recontructed that ascending fishes are able to reach the biggest part of those areas that are relevant as habitat are for the young fishes. For improvement of downstream migration there was a new near to the surface bypass installed at the small hydropowerstation of Perleberg in 2003. Although a final functional evalutation of the downstream channel is missing first results of an examination tend towards the assumption that especially smolts have a considerable improvement for downstream migration. A further improvement for downstream migration was the turning off of the hydropowerstation in Putlitz , ordered by the rural destrict of Prignitz, in the year 2003, which was run for 10 years without legal admission. Unfortunately some near-to-nature sections in the upper reaches are not in access for ascending salmon and seatrouts. This applies to the main run of the Stepenitz above the Pulitzer millweir and to the Doemnitz above the Kathfelder mill at Pritzwalk. At the last mentioned location there is no passage without damage. A solution to these problems failed due to little interest in cooperation by the conductors of the facilities and owners of the buildings.
Despite of the remaining problems the involved fishermen and fishery scientists are convinced that within the realization of the EU-waterframework directive the conditions for the existence of salmon and seatrout can be built up in such a manner that the natural reproduction will be based on a sufficient number of adult spawners. In intermediate terms the goals is to produce the necessary stocking fishes out of own returners und if there is a further positive development to permit a responsible use of the resource for the fishermen.
Moreover there is a smoltmonitoring were Uli Thiel
gave the following report : On the picture below the colleagues of the IfB
just finished the installation of the smolt trap at the mill weir at
The catching box was seperated into two parts to separate the smolt into two
groups (bypass/turbine or fishway). This worked very well in our pre-attempt in mai 2007 .
The Stepenitz in Perleberg parts into three arms , of which two are of
interest for smoltmigration. Because of the use of hydropower most water
flows through the millweir so that the smolt trap was installed here. The
turbine outlet is on the right side - seen in flow direction. The adjustable
that is only seldom overflown is used to discharge floods, lies in the
middle of the channel and in flowdirection on the left side there is a
fishladder (slot width 20 cm). The barrage in the tailrace is kept by
a sluice. The turbine outlet lays above at right angle to the flow direction
of the Stepenitz and has a rolling screen (meshwidth 5x15 mm) . The upper
edge of the turbine sluice has a cut-out where about 80 l/s flow out over an
open metal chute into the tailrace. Smolts and other surface near migrating
fishspecies find this hole in the turbine sluice quite quickly when they are
not able to pass the rollscreen. The facility was built with up by means of
the country fishing association as a provisionary solution in 2003. At that
time we were happy to have the permission by the environmental office of the
country to modify it barrage at all. Since then there were merely found dead
or injured fishes at the rollscreen. Eventually the flow regime in the
bypass chute is a little bit to strong and there should be modifications.