Ahlhorn fish ponds

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Ahlhorn fish ponds

IUCN Category IV - Habitat / Species Management Area

Ahlhorn fish ponds 02.jpg
location Northeast of Cloppenburg , southwest of Großenkneten
surface 437 ha
Identifier NSG WE 216
WDPA ID 162048
Geographical location 52 ° 56 '  N , 8 ° 9'  E Coordinates: 52 ° 55 '33 "  N , 8 ° 8' 39"  E
Ahlhorn fish ponds (Lower Saxony)
Ahlhorn fish ponds
Sea level from 24 m to 37 m
Setup date 04/12/1993
administration NLWKN
f2

Ahlhorner Fischteiche is a 465 hectare nature reserve (official registration number: NSG WE 216) in the west of the Wildeshauser Geest nature park in Lower Saxony , which is located on both sides of the Lethe on the southwestern edge of the Oldenburg district and on the eastern edge of the Cloppenburg district. The ponds of the NSG Ahlhorner Fischteiche are located in the areas of the communities of Großenkneten and Emstek . They form part of the Fauna-Flora-Habitat- Area 012 ("Sager Meer, Ahlhorner Fischteiche, Lethetal") of the European Union. A small section west of the Lethe in the northwest of the NSG belongs to the municipality of Garrel in the district of Cloppenburg.

historical development

The Grand Duchy of Oldenburg was in 1900 the only country in the German Reich was, that was not a member of the German Committee on Fisheries and therefore no means the kingdom to promote inland fishing. At that time there were larger heather and wasteland areas over sand in the Sager Heide , which had little or no yield and were owned by the Landeskulturfonds. Its favorable location and the almost neutral water quality of the Lethe, which grazes the area, provided the basis for the creation of fish ponds. After the first pond, the "Rüdersee", had been created in a springy depression in 1884, in 1898 the fish management master Riggert, administrator of the Oeseder fish breeding establishment, was commissioned to draw up an expert opinion on where a pond management could be established in the Grand Duchy of Oldenburg. From December 19 to 24, 1898, Riggert toured the Grand Duchy with a delegation. The commission chose Ahlhorn. Until 1901 ponds were created at the "Katzenkopf", southwest of the Lethe, on the road to Beverbruch and in the Sager Heide. The main construction phase took place between 1906 and 1929. After completion, the project comprised 54 ponds with a water surface of 200.5 hectares. Today, due to a lack of water, only around 35 ponds with a water surface of approx. 120 hectares are managed.

In 1984 the pond farming area was declared a bird sanctuary . However, this status was revoked in 2000. Since 1993 the area "Ahlhorn fish ponds" is under nature protection. In the same year the pond economy was protected as a "hydraulic cultural monument " by a resolution of the Lower Saxony monument protection authority .

On the Buhlertsberg in the center of the ponds stands the Ahlhorn log house, a Protestant youth home since 1946 . Construction began in 1934, in 1937 it was expanded into a Gau comradeship home and in 1945 it was even used as a prison camp for the British Army .

Natural structure

The largest ponds are (from west to east) the swan lake, the reed pond, the Kirchsee, the Helenensee and the Hubertusteich. A little south of these ponds, in the eastern part of the Baumweg state forest, are the Great and Small Dianasee, which are, however, natural bodies of water. They are not part of the Ahlhorn fish ponds. The ponds are embedded in mixed forests. They are fed with water by the Lethe, which flows through the nature reserve and is a left tributary of the Hunte . In the area of ​​the Ahlhorn fish ponds, the Lethe is interrupted by four barrages, which serve as reservoirs for the water supply. The ponds are at different heights and are connected to each other and to the Lethe by a network of canals. Their water can be drained and replenished by mechanical devices.

  • Kirchsee with St. Petri Chapel and buildings of the block house complex

  • Helenensee with adjacent mixed forest

  • Dianasee in the eastern section of the Staatsforstes Baumweg

  • Barrage of the Lethe above the Dianaweg

Boulder complex

The "12 Apostel" boulder complex , a natural monument, is located in the nature reserve . What is up with the large erratic boulders that only look a little out of the earth has not yet been clarified exactly. In 1950 it was assumed that it was a cult site from the late Stone Age or the older Bronze Age .

Economic use

Fishing industry

Farm shop of the State Pond Management Ahlhorn

In 1907 the regular operation of the state pond management began. In 1931 it was added to the Ahlhorn Forestry Office, of which it is part of the business today. The pond management includes an extensive, listed building complex.

The ponds are regularly dammed, drained and, if necessary, also desludged and weeded. Since only about 15 percent of the ponds are covered with water after fishing in autumn, the remaining pond bottoms are exposed to frost in cold winters, and the other ponds are not flooded again until spring.

Every year 35 to 50 tons of carp , tench , pikeperch and trout are fetched from the Ahlhorn fish ponds. Eilert Tantzen rates the earnings situation as "always very tense from the start". Already in the first few years the pond floors had to be fertilized, because naturally not enough fish food could grow there. However, the stocking fish from the Ahlhorn fish ponds are very popular with customers because they are free from fish diseases.

forestry

The state pond management is part of the Ahlhorn Forestry Office. The Baumweg district forester is responsible for maintaining the forest at the Ahlhorn fishponds.

Water management

St. Petri Chapel on the Kirchsee

In the immediate vicinity of the nature reserve, the Oldenburg-Ostfriesische Wasserverband (OOWV) operates 27 wells to supply the Oldenburg region with drinking water .

Extracurricular meeting places and learning locations

Houses of the youth meeting place Blockhaus Ahlhorn

Log house with St. Petri chapel

The log house, which was taken over by the Evangelical Lutheran Church in Oldenburg in 1946 , has since been primarily run as a meeting place for young people. However, in recent years the facility has increasingly opened up to informal groups and individual travelers.

The St. Petri Chapel has been located near the log house complex since 1982. This is a " Bartning-Notkirche (Type D) ", which was originally built in 1950 in Steinfeld (Oldenburg) and was moved in 1982 to the area of ​​the Ahlhorn fish ponds. A total of 19 such emergency churches of type D, designated as community centers , were built in Germany after 1945 in the same functional style in order to provide Protestant communities with rooms for church services, but also for community work. The organ in the chapel dates from 1990. The first poplar figure of Peter was placed in front of the chapel in 1992; as it weathered quickly, it was replaced by a new figure in 2009.

Ahlhorn Forest Education Center

The Ahlhorn Forest Pedagogy Center, an extracurricular location for environmental education, is located near the log house between several Ahlhorn ponds. The forestry office is responsible for the work and experience-related part during the students' stay. Around 20,000 children and young people from all northern federal states spent four decades here under the supervision of the respective youth forest home manager and under the guidance of forest managers.

gastronomy

Lethetalscheune

To the south of the parking lot at the fork in the road to the pond farm, the inn "Zum Karpfen" stood until 1987. It was demolished in 1987 because of its inefficiency and construction defects. As a gastronomic alternative, the café in the Lethetalscheune is available today on event days of the Teichwirtschaft.

Former inn "Zum Karpfen" near the Ahlhorn fish ponds

natural reserve

The NSG Ahlhorner Fischteiche is a retreat and habitat for many rare plants and animals.

plants

In terms of the Habitats Directive, the beach lions and dwarf rush communities found in geest lakes such as the Ahlhorn fish ponds are considered worthy of protection.

Botanists were able to identify 237 vascular plants and 35 species of moss in the nature reserve . According to the red list of endangered vascular plants for Lower Saxony and Bremen, 27 of the aquatic and bank plants occurring in the area of ​​the Ahlhorn fish ponds are considered endangered. In the rear area of ​​the dams there are considerable layers of peat in sectors , which are overgrown with gale bushes in places .

The management measures of the pond economy make it possible that the periodically drained ponds, especially in dry years, pioneer plants such as z. B. frog spoon and two-tooth , offer good development opportunities.

Animals

In the early years there were efforts on the part of the fisheries directors of the pond industry to “keep fish eaters” (i.e. herons , divers, coots , water rats , otters , foxes and wild ducks ) short. In 1931, 108 herons were shot. Hunting fish-eating land animals in the nature reserve is only permitted in exceptional cases.

fishes

For occurring in the nature reserve lamprey is a year-round ban on fishing.

Birds

Over 200 species of birds have been spotted in the Ahlhorn fish ponds nature reserve , including the red-necked grebe , the blue -necked blue duck , the teal and the black stork .

In 2002, the "Landesverband Bürgerinitiativen Umwelt [environmental protection] (LBU) Lower Saxony" opposed the request of the Ahlhorn Forestry Office to be allowed to shoot 30 cormorants in the Ahlhorn pond management area between 2002 and 2005 . The LBU justifies this with the fact that "damage to nature and the landscape [...] is not to be expected if the project is not carried out".

It is not one of the original tasks of nature conservation to promote fish ponds, to take care of measures to regulate the stocks of species, or to take care of the welfare of nesting and edible fish. The " Biologische Schutzgemeinschaft Hunte Weser-Ems " (BSH) points out, however, that there is a risk that shallow water areas will silt up and become overgrown if professional fishing is given up there, and that then roosts for other water-dependent birds such as divers, ducks, sawaws and Ospreys were missing. At the same time, the accompanying fauna bound to the open water is eliminated: toads , frogs and newts ; Dragonflies and other aquatic insects, but also other invertebrates such as single-celled organisms , sponges , hollow animals , bryophytes and annelid worms would be affected.

While the loss of yield due to gray herons and other fish-eaters who hunt their food in the bank area could have been compensated for economically so far, extensive farms such as in Ahlhorn are threatened with extinction, since cormorants have also hunted in the open water. From this, the BSH draws the conclusion: "Even in nature reserves, the settlement of cormorants in the immediate vicinity of areas that are important for fishing should not be encouraged, but rather prevented from the outset." The one-sided protection of the two large fish-hunting bird species (herons and cormorants) According to BSH, the Ahlhorn ponds would be at the expense of those other vertebrate species, whose populations are of great importance for the preservation of a particularly endangered fauna.

Amphibians

Of amphibians were found in the ponds: water frog ( Rana esculenta ), common frog ( Rana temporaria ), tree frog ( Hyla arborea ), common toad ( Bufo bufo ), the natterjack toad ( Bufo calamita ) and great crested newt ( Triturus eristatus ), marsh frog ( Rana ridibunda ) Pool frog ( Rana lessonae ) Moorfrosch ( Rana arvalis ), garlic toad ( Pelobates fuscus ) and thread pig ( triturus helveticus ).

Threats to the ecosystem

The changes in the management of the land on the upper Lethe in the last few decades have had a significant impact on the ecological processes in the pond area. Over the years the water donation from the upper Lethe has decreased significantly. Due to the intensive agriculture in the upper Lethe area, the river has been heavily polluted with nutrients and pesticides for many years, which cause lasting damage to nature in the nature conservation and FFH area Ahlhorn fish ponds. This leads to algal blooms and subsequent siltation and declining water quality of the ponds. This damages the food chain and impoverishes flora and fauna. A sharp decline in the breeding pairs of water birds can already be seen.

The situation is exacerbated by the extraction of groundwater by the Oldenburg-Ostfriesischer Wasserverband (OOWV), which operates wells in the immediate vicinity of the Lethe and the state pond management. This leads to increased water seepage into the pond floors. In April 2009, the water shortage in the pond area was so severe that fresh water was required to ensure the young trout breeding.

A major problem is the ocher formation of the surface water of the Lethe, especially below the Lethetalsperre. In March 2009, the leaders of the "Hunte 25" project suggested reducing nitrogen inputs into the Lethe as an "effective and sustainable measure".

In November 2008, the “ Biological Protection Association Hunte Weser-Ems ” applied for the catchment area of ​​the Lethe in its source area to be placed under nature protection in order to protect the Ahlhorn fish ponds. The district of Cloppenburg as the lower nature conservation authority rejected the application. In November 2010, the BSH criticized the state of Lower Saxony for failing to meet its obligations under Article 6 of the Habitats Directive by failing to take effective measures against the introduction of nutrients and chemicals via the Lethe into the fish ponds and against excessive groundwater abstraction by the OOWV seize.

The situation worsened in the 2010s: the inflows from the Lethe into the ponds contained 37 milliliters of nitrate per liter in 2017, the groundwater even 67 milliliters per liter, as the areas in the upper reaches of the Lethe are still over-fertilized. A large part of the nitrate remains in the ponds, which can be seen from the fact that the water of the Lethe below the fish ponds only has a nitrate content of 5 milliliters per liter. The algal bloom caused by the eutrophication of the ponds in warm summers destroys a large part of the oxygen in them. As a result, animals and plants in the pond water are killed and rare plant species are replaced by "common species". The ponds would be misused as a "sewage treatment plant".

In 2019, the head of the forestry office, Regina Dörrie, called on the nature conservation authorities in the districts of Oldenburg and Cloppenburg to fulfill their official duties and to initiate measures to protect the nature conservation ponds from an "exit" due to a lack of water and oxygen. Otherwise, it is to be feared that the protection status of the FFH area will be withdrawn.

Individual evidence

  1. ↑ Hubert Fenske: Ahlhorn fish ponds. 100 years of near-natural biotopes made by human hands (PDF; 267 kB). Naturschutzverband Niedersachsen eV (NVN) / Biological Protection Association Hunte Weser-Ems. North German biotopes - protection and development . Issue 23 p. 1
  2. ↑ Eilert Tantzen: 100 years "Ahlhorner Fischteiche" , in: Yearbook for the Oldenburger Münsterland 2006 , published by the Heimatbund for the Oldenburger Münsterland, Cloppenburg 2006, p. 281
  3. ↑ Bernd Rothmann: 12 Apostles, Ahlhorn
  4. ↑ The "12 apostles" give riddles  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. Northwest Newspaper . August 8, 2008@1@ 2Template: Dead Link / www.nwzonline.de  
  5. ↑ Hubert Fenske: Ahlhorn fish ponds. 100 years of near-natural biotopes made by human hands (PDF; 267 kB). Naturschutzverband Niedersachsen eV (NVN) / Biological Protection Association Hunte Weser-Ems. North German biotopes - protection and development. Edition 23 p. 3
  6. ↑ Eilert Tantzen: 100 years "Ahlhorner Fischteiche" , in: Yearbook for the Oldenburger Münsterland 2006 , published by the Heimatbund for the Oldenburger Münsterland, Cloppenburg 2006, p. 278ff.
  7. ^ Homepage of the Ahlhorn pond farm
  8. ↑ Answer of the state government to the "Small question from Members Renate Geuter and Axel Brammer ": Teichwirtschaft Ahlhorn - A natural oasis in the northwest - How much longer? Lower Saxony State Parliament - 16th electoral term; Printed matter 16/2341. January 19, 2010. p. 3
  9. ↑ Dirk Fass: The block house church St. Petri to the fish ponds . In: Heimatblätter (supplement to the Oldenburgische Volkszeitung ). No. 2/2012. April 14, 2012, p. 15
  10. ↑ Lower Saxony State Forests: Forest Pedagogy Center Ahlhorn ( Memento of the original from October 21, 2014 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . P. 16 @1@ 2Template: Webachiv / IABot / www.landesforsten.de
  11. ↑ Klaus Derke: Jugendwaldheim excellent. In: Nordwest-Zeitung. September 24, 2005, accessed on June 12, 2019 (Environment Prize of the Nature Foundation goes to Ahlhorn institution).
  12. ↑ nwzonline.de February 18, 2012: Schoolchildren should research forests Forestry office and GAG want to develop learning content
  13. ↑ Eilert Tantzen: 100 years "Ahlhorner Fischteiche" , in: Yearbook for the Oldenburger Münsterland 2006 , published by the Heimatbund für das Oldenburger Münsterland, Cloppenburg 2006, p. 282
  14. ↑ Lower Saxony State Forests: Forest Nature Conservation in the Lower Saxony State Forests - Ahlhorner Fischteiche ( Memento of the original from July 10, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.landesforsten.de
  15. ↑ Hubert Fenske: Ahlhorn fish ponds. 100 years of natural biotopes made by human hands (PDF; 267 kB). Naturschutzverband Niedersachsen eV (NVN) / Biological Protection Association Hunte Weser-Ems. North German biotopes - protection and development. Edition 23 p. 4
  16. ↑ Hubert Fenske: Ahlhorn fish ponds. 100 years of near-natural biotopes made by human hands (PDF; 267 kB). Naturschutzverband Niedersachsen eV (NVN) / Biological Protection Association Hunte Weser-Ems. North German biotopes - protection and development. Edition 23 p. 3
  17. ↑ Eilert Tantzen: 100 years "Ahlhorner Fischteiche" , published by the Heimatbund for the Oldenburger Münsterland, Cloppenburg 2006, p. 280
  18. ↑ State Association of Citizens' Initiatives Environmental Protection (LBU) Lower Saxony: Fax to the Weser-Ems district government (PDF; 214 kB). June 28, 2002
  19. ↑ Biological Protection Association Hunte Weser-Ems eV: Cormorants in the interior of Lower Saxony (PDF; 628 kB) p. 2f.
  20. ↑ Biological Protection Association Hunte Weser-Ems eV: Cormorants in the interior of Lower Saxony (PDF; 628 kB) p. 7
  21. ↑ Biological Protection Association Hunte Weser-Ems eV: Cormorants in the interior of Lower Saxony (PDF; 628 kB) p. 10
  22. ↑ Biological Protection Association Hunte Weser-Ems eV: A balance between fish and their enemies is necessary. Otherwise, BSH sees the future of the Ahlhorn pond economy in jeopardy March 7, 2000
  23. ↑ Antje and Fritz Wadehn: The amphibians of the Ahlhorn fish ponds ( Memento of the original from February 23, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Blockhouse letter No. 23 . 1979 @1@ 2Template: Webachiv / IABot / www.leb-grossenkneten.de
  24. ↑ Teichwirtschaft Ahlhorn - A natural oasis in the northwest - How much longer? Small question from the MPs Renate Geuter and Axel Brammer (SPD). Lower Saxony State Parliament - 16th electoral term; Printed matter 16/2341. January 19, 2010. p. 1
  25. ↑ hunte 25: What actually is ochering? ( Memento of the original from April 23, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.hunte-25.de
  26. ↑ OOWV / hunte 25 / DHI-WASI: Implementation of the European Water Framework Directive Integrated modeling of river basins - input of matter , currents and transport. Development of an integrated surface groundwater model, focus area Obere Lethe as part of the model project Hunte 25 ( Memento of the original from April 23, 2014 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 13.3 MB). Final report March 2009. pp. 15–18, 26–40 and 145 @1@ 2Template: Webachiv / IABot / www.hunte-25.de
  27. ↑ Biological Protection Association Hunte Weser-Ems eV: Application of the BSH for nature protection for the Obere Lethe area and tributaries in favor of the FFH area Ahlhorn fish ponds . April 3, 2009
  28. ↑ Appeal: More nature protection at the border - tough words in the direction of Cloppenburg . District newspaper . October 28, 2009
  29. ↑ Directive 92/43 / EEC of the Council of May 21, 1992 on the conservation of natural habitats and of wild animals and plants (OJ L 206 of July 22, 1992, p. 7) (PDF; 200 kB)
  30. ↑ Biological Protection Association Hunte Weser-Ems eV: More water - less sludge for the Ahlhorn fish ponds! November 1, 2010
  31. ↑ Soeke Heykes: Species diversity in Ahlhorn fish ponds threatened . nwzonline.de. May 31, 2019
  32. ↑ Jacqueline Schulz: State forests sound the alarm: Ahlhorn ponds are extremely polluted with nitrates . weser-kurier.de . June 6, 2019
  33. ↑ Rainer Städing: Ahlhorner Teiche: Measurement results confirm loss of biodiversity . Lower Saxony state forests. 3rd June 2019
  34. ↑ Hubert Kreke: Fish ponds before the nitrate exitus . Oldenburg People's Newspaper. June 7, 2019. p. 22
  35. ↑ Fish ponds are threatened with their protection status being withdrawn . Oldenburg People's Newspaper. June 14, 2019. p. 20

literature

  • Eilert Tantzen : 100 years "Ahlhorner Fischteiche" , in: Yearbook for the Oldenburger Münsterland 2006 , published by the Heimatbund for the Oldenburger Münsterland, Cloppenburg 2006, pp. 267–285
  • Günter Alvensleben: The Ahlhorner Fischteiche - A nature reserve with a unique selling point in Lower Saxony , in: Kulturland Oldenburg , published by the Oldenburg landscape , issue 175 (issue 1/2018), p. 36f. ( online )

Web links

Commons : Ahlhorner Fischteiche  - Collection of images, videos and audio files