Life Nature Project
LIFE2002NAT/D/8458
| Life Nature Project LIFE2002NAT/D/8458 |
Life-Project: "Large freshwater mussels Unionoidea in the border area of
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| Pictures and Reports | |
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Construction of near-natural silt traps  The
establishment of near-natural silt traps at the mouth of the tributaries
aims at reducing the fine sediment load in the mussel rivers at normal
water level. At the same time, the river should allow for the passage of
fish as well as coarse sediment at floods. The sediment of the receiving
stream is renewed by this material.
At eight tributaries the projected silt traps were built in autumn 2004. According to the stream flow of the tributaries and the amount of sediment expected, the size of the silt trap as a hole and the number of accumulation basins connected in series were varied. An ongoing evaluation will show whether the traps function as hoped for.
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Establishment of paved fords  A
cattle herd (suckler cows) is kept on both sides of the mussel stream.
At change of pasture the animals are driven through the river. Fords are
also used as a watering places. Around the fords the sward is trampled
and destroyed, inviting soil erosion. To avoid the loading of the stream
with silt the fords were paved. Now the functioning of the fords as watering
places is surveyed: Firstly, do the animals accept the paved fords? Secondly,
will the herd lair near the watering places, polluting the stream with
silt and dung? In this case it will be tried to establish cattle watering
tanks in distance to the stream.
Support of the recruitment of mussels in optimized habitats A) Freshwater pearl mussel: Release of young mussels in cleaned sediment  The
siltation of the river bed prevents that young freshwater pearl mussels
grow up. The juvenile mussels live in gaps between the river pebbles (interstitial).
Siltation causes a lack of oxygen in these microhabitats. Hence short stream
sections were cleaned from silt. To support the recruitment of the mussels,
young mussels were collected from artificially infected host fish and released
in these cleaned sections of the mussel streams.
Mechanical silt removal was carried out in six stream stretches with a length of 20 to 30 metres each. Before the cleaning procedure, the stretches were searched for adult mussels to be put aside and brought back after the cleaning. |
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 The
sediment cleaning was performed in a way that keeps the washed-out silt
outside the stream: The top sediment layer was taken out of the stream
bed with an excavator and washed with a fire hose on a trailer near the
bank. The water and the washed-out silt was allowed to run off into the
meadow near the bank. Afterwards coarse sand, gravel and stones were put
back into the river. If necessary, material from a nearby quarry was mixed
in to replace the washed-out silt and to provide the original quantity
of sediment.
The sediment was examined before and after the treatment as to its content of silt and sand. This examination will be repeated subsequently to investigate how quickly the cleaned sediment will silt up again. |
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Weight percentage of sand (light columns) and silt (dark columns) in sediment samples before the sediment cleaning at six different sites (“Probestellen”). Diamonds show the percentage of organic material in the silt. |
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Weight percentage of sand (light columns) and silt (dark columns) in samples of cleaned sediment at six different sites (“Probestellen”) and in added quarry material (“Zuschlag”). Diamonds show the percentage of organic material in the silt. |
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| In early summer 2004 brown trout infected with pearl mussel glochidia were exposed for a short time in bow nets in the cleaned river sections. Thus, the young mussels would fall off in the optimised habitat. The bulk of the artificially infected fish was kept in a plastic tank to enable the collection of young mussels falling off the host fish. About 120.000 young mussels were collected and released directly into the sediment of the cleaned river sections. As to our experience this is an outstanding yield. The release sites were marked for later monitoring of growth and survival of the juvenile mussels. | |
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B) Common river mussel: Optimised habitat for the host fish and artificial infection  In
the area inhabited by the common river mussel the stream was rather poorly
structured, providing insufficient shelter for small fish. To improve the
habitat for small fish and especially for minnow (Phoxinus phoxinus),
the main host fish of the common river mussel, some snaggy spruce trees
were fixed in the river, and shallow bassins were established at the banks.
For small fish, both trees and bassins offer sites that are inaccessible
for predators, thus functioning as spawning grounds and sheltered locations
for juvenile fish. An increased and stabilised abundance of minnow will
improve the chances of a successful natural infection with larvae of the
common river mussel.
Since the population of the common river mussel is small and elderly, the recruitment is additionally supported by artificial infection of host fish. In early summer 2004 mussel larvae (glochidia) of gravid females were collected. Minnows were captured by electrofishing in a section of the mussel river. The fish were infected with the larvae and then set free in the stream section inhabited by the adult mussels. Thus, it was estimated, about 65.000 young mussels have been released in the river. |
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Electrofishing:
How good is the population of the host fish? (October 2003)
 In
October 2003, and again in November 2005 and Juni 2007, the mussel rivers were electrofished at six stretches of 100
m each to monitor the fish populations. The fishing was done in cooperation
with the Technical University of Munich/Weihenstephan and the fishery consultancy
of the district of Upper Franconia.
Fortunately, the fishing showed a good survival and recovery of fish populations after the severe drought of the summer of 2003. In the upper stream section of the project area a sufficient abundance of host fish for the pearl mussel, namely young brown trouts, was found (see figure below: “Fischartenspektrum Oberlauf”). The low number of fish species is typical for pearl mussel streams, being very poor in nutrients. In the lower section a much higher number of species was found. However, the population of brown trout is smaller (see figure below: "Fischartenspektrum im Unterlauf"). On the other hand, a surprisingly high abundance of minnows was observed.
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| Visits at external
projects
July 2003: Pearl mussel conservation in the Lutter/Lachte-system in Lower Saxony After two decades of intensive efforts for the conservation of the freshwater pearl mussel, young mussels grow up again in high numbers.  
Dr. Reinhard Altmüller (Lower Saxony, regional office for ecology), Dr. Volker Buddensiek and Reiner Dettmer (f.l.t.r.) present four- to ten-year-old mussels on an excursion with experts from the Bavarian LIFE-Nature project. Pictures by Susanne Hochwald, Reinhard Altmüller Main conservation measures carried out with a high overall
expenditure, include
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August 2003:
Visit at the Belgian LIFE-Nature project Nr. LIFE2002NAT/B/8590 for the
conservation of the freshwater pearl mussel
 On
invitation of the Ministry of the region Wallonne, a workshop took place
at the Centre de Recherche de la Nature des Forêts et du Bois de
Gembloux with associates of projects for the protection of the freshwater
pearl mussel in France, Belgium, Luxembourg, Austria and Germany. During
an excursion the project areas of the Belgian LIFE-Nature project Nr. LIFE2002NAT/B/8590
„Conservation of habitats of pearl mussels in Belgium“ were visited.
The picture shows Christine Schmidt from the Bavarian LIFE-Nature project (left) with the Belgian colleagues Gregory Motte (front) and Stefan Bocca (right). The mussel populations of this region exist in the catchment areas of the rivers Sure, Rulle and Our in the low mountain range Ardennes-Hohes Venn-Eifel. In some streams the freshwater pearl mussel is coexistent with the common river mussel. |
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Informations on the LIFE-Nature project in Belgium at www.mrw.wallonie.be/dgrne/sibw/life/mouleperliere |
The endangering of the large freshwater mussels in Belgium
shows a lot of parallels to the situation in the system of the Südliche
Regnitz. Additionally, extensive clear cuttings pollute the mussel rivers
in Belgium.
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November 2003:
visit at the French Parc du Morvan
 On
a one-day excursion Pierre Durlet (left) of the Parc naturel regional du
Morvan led Christine Schmidt (right) and Dr. Robert Vandré to pearl
mussel streams in the Parc regional du Morvan in Burgundy, France.
The streams have in parts a loose, nearly silt-free ground. After shaking a sediment sample with water in a graduated cylinder, only a minimal layer of silt deposits on the granite gravel.
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November 2004: Specialist Meeting and Excursion in Irelad On 16th und 17th of November 2004 members of the LIFE-project joined the workshop “Freshwater Pearl mussel restoration” of the UK Biodiversity Action Plan Steering Group for freshwater pearl mussels in Belfast. During the meeting British, Irish, Scottish and Welsh experts discussed the status and problems of mussel conservation. The German participants stressed that the restoration of habitats must not be neglected in favor of artificial mussel recruitment. After the meeting the group vistited the Ballinderry Fish Hatchery, where a promising attempt to breed pearl mussels is made by the University of Belfast (compare www.fwr.org/environw/sr0202.htm). The breeding facility shows strong parallels to a freshly cleaned mill stream, which leads to valuable suggestions for the sediment cleaning and the artificial mussel stream of the LIFE-Nature project. The Irish mussel experts Evelyn Moorkens and Ian Killeen kindly invited their German collegues R. Altmüller, V. Buddensiek and R. Dettmer, as well as C. Schmidt and R. Vandré from the LIFE-Nature project, to visit Irish mussel rivers. |
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| In County Connemara reproducing populations
were visited. Despite of the pouring rain the group had a close look at
the mussels and their habitate and discussed conservation issues. In this
region, the mussel populations are endangered by plantations of spruce
and pine, since extensive clear cutting and the use of fertilizers lead
to the loading of lakes and rivers with nutrients.
In County Kilkenny the situations is more alike that of the area of the LIFE-Nature project: Intensive agriculturing in the catchment of the mussel river is the main cause for decline of the last population of Margaritfera durrovensis.
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Pastures of cattle on the river banks cause erosion, thus contributing to the siltation of the mussel habitats. |
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| Alle Fotos, die nicht anders gekennzeichnet sind, stammen von Christine Schmidt und Robert Vandré (Schmidt & Wenz GbR) und unterliegen dem Copyright. Sollten Sie daran interessiert sein, diese Fotos in irgendeiner Weise als Reproduktion oder digital zu verwenden, setzen Sie sich bitte mit den Fotografen in Verbindung |
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These
are sediment conditions are hoped to be re-established in the system of
the Südliche Regnitz on the long run. Still, there are problems with
the reproduction of mussels in the Morvan, too. Presumably, the reason
is that the host fish population is damaged by paved or trampled river
banks and extensive ponds, the latter leading to strongly elevated water
temperatures in summer. Since 2004 these problems are addressed by the
LIFE-Nature project LIFE04 NAT/FR/000082 “Headwater streams and faunistic
Heritage associated”.
Discussion
on the cause of the mud content of the river containing the last population
of Margaritifera margaritifera var. durrovensis in Ireland (from left to
right: Volker Buddensiek, Robert Vandré, Ian Killeen, Reinhard Altmüller,
Rainer Dettmer)