North Sea Bill

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North Sea Bill
"The beak, Coregonus oxyrhynchos". Plate 22 from Emil Walter: Our freshwater fish. Leipzig: Quelle & Meyer, 1913.

"The beak, Coregonus oxyrhynchos".

Plate 22 from Emil Walter: Our freshwater fish. Leipzig: Quelle & Meyer, 1913.

Systematics
Cohort : Euteleosteomorpha
Order : Salmonid fish (Salmoniformes)
Family : Salmon fish (Salmonidae)
Subfamily : Coregoninae
Genre : Coregonus
Type : North Sea Bill
Scientific name
Coregonus oxyrinchus
( Linnaeus , 1758)

The North Sea beak ( Coregonus oxyrinchus ), also known as Rhine beak, Houting and Kleine Schwebrenke, is a taxonomically controversial fish species from the salmon fish family . It belongs to the genus of whitefish, whitefish or whitefish ( Coregonus ). The species is probably in the 1940s due to water pollution extinct . According to some experts, it survived in a small Danish population. Stocking fish obtained here were used for (re-) naturalization in various water systems. Most experts believe, however, that these animals really belonged to a different species, the Baltic sea beak Coregonus maraena .

The North Sea bill was voted fish of the year in Germany in 1999 .

features

Head drawing

The delimitation of the species within the genus Coregonus is one of the most difficult tasks in the taxonomy of fish. These are young species, presumably only differentiated for a few 1000 years after the end of the Vistula Glaciation , which can usually freely hybridize with each other on contact . Under the species name Coregonus oxyrinchus , different taxonomists have existed in the course of time, different species or other taxonomic units, which have been characterized and distinguished from one another by different features . The following illustration is based on the new description of the species by Jörg Freyhof and Christian Schöter in 2005.

The North Sea beak is therefore a large species of whitefish with an elongated, laterally strongly flattened body. It has the typical body shape of all vendace. The snout is noticeably elongated like a nose and protrudes far beyond the front edge of the lower jaw. This extension consists of soft, spongy tissue and is usually not preserved in preserved animals. As a result of the lengthening, the mouth opening is shifted to the abdominal side of the head (ventrad), the upper and lower jaw both extend backwards to behind the front edge of the eye, often to the center of the eye. The upper jaw extends further forward than the lower jaw. The eyes are relatively large, their diameter is about 0.7 times the distance between the eyes. The edge of the dorsal fin is indented (concave).

The most important feature to differentiate it from other species is, as is often the case within the genus, the number of spine thorns on the gill arch . This depends, among other things, on the diet, species that primarily feed on plankton by filtering have more and narrower thorns. On the first gill arch, 38 to 46, an average of 40 spines, are formed in this species. Coregonus mareana has only 25 to 35 spines. However, Danish researchers in particular point out that the characteristics used are variable and also depend on the age of the fish (and thus on the growth rate and the reproductive cycle). The morphological units differentiated on the basis of the gill spines do not necessarily correlate with genetically related groups. According to all older information, the species cannot be distinguished from the Baltic bill in any way, neither in its color nor in its size.

distribution

The North Sea beak lived in the estuaries and lower reaches of the Rhine , Meuse and Scheldt rivers , as well as in southern England, of which only three finds from the 19th century, from the River Medway , from Lincolnshire and from Chichester , are available. The species occurred in the rivers and the offshore estuaries , in brackish water and seems to have avoided real marine conditions, at least there are no documented animals or reports from such areas.

Coregonus populations of unclear species affiliation also lived in the Elbe and other bodies of water that drain into the eastern North Sea. Here all populations, around the same time as those in the western North Sea, are extinct - with one exception: in the Vidå (name variants: Vidau, Vide Å, Vide Au) in the Danish Sønderjylland , the only migratory moray population in the North Sea has been preserved. However, this stock also showed sharply falling numbers in the post-war period and threatened to become extinct. Animals obtained here and reproduced in breeding tanks were released into a number of European river systems, including the Rhine, to establish new populations. Many researchers and conservationists refer to these new populations as "North Sea billets", but it is very debatable whether they belong to the same evolutionary unit (or species). Since there is no genetic data from the North Sea beak, in the sense of Freyhof and Schröter, the question is open and it may never be possible to finally clarify it.

Way of life

The way of life of the North Sea beak as an extinct species can only be given on the basis of the sparse information in the works of contemporary ichthyologists or limnologists. Better data are available for the surviving populations of migratory moraines, in particular the Baltic sea beak and the populations presumably belonging to it, which can be traced back to animals from the Danish Vidå, but these can only be transferred with reservations. Due to the closely spaced gill spines, a plankton-eating way of life, as a filter feeder, is developed for the species, analogous to the surviving vendace with this characteristic.

North Sea billets were anadromous migratory fish, that is, they lived in the sea or in the brackish water of the estuaries, but climbed into the rivers to spawn. This is where they differ from lake vendace such as the morphologically very similar blue vendace ( Coregonus wartmanni , formerly mostly called Coregonus lavaretus ) of Lake Constance and a number of species endemic in northern German lakes such as the Stechlin vendace ( Coregonus fontanae ). The authors of the 19th century stated that they had risen to spawn in large numbers as far as Wesel , and occasionally even as far as the Middle Rhine near Strasbourg. The Danish population (whose species affiliation is disputed) consists of animals that spawn several times in their individual lives of around 10 to 12 years, i.e. not like salmon die after reproduction. This is also assumed for the North Sea beak of the Rhine.

The decline in the beak of the Danish population was analyzed in more detail in order to initiate protective measures. The information is presumably transferable to the very closely related “real” North Sea beak. After almost extinction, in 2000, despite stocking, the population had grown to only around 6000 to 7000 adult individuals. Spawning habitats for the species in Denmark are clean waters with a water level of about 4 to 10 meters, with a gravel bottom and rich aquatic plants. The animals migrate to the spawning waters from November to December. The eggs are simply released into the open water, they are sticky and stick to stones or water plants. They hatch in February or March. Young fish can be driven into still water areas such as floodplains or reed beds with the current. They feed on zooplankton. They cannot survive in water of higher salinity.

die out

In the Red List of Threatened Species of IUCN is the houting as "Extinct" ( Extinct listings) because since 1940, no evidence has been documented for the occurrence of the species in its native range. This view is also followed by the Red List of European freshwater fish.

The beak in the North Sea were economically important food fish until the beginning of the 20th century. Fishing in the Rhine was concentrated from August to November. Catch figures up to 1910 are not available. 5000 kg were caught in 1917, 1000 kg in 1921, 100 kg in 1933, 3 kg in 1939.

Commercial fishing declined rapidly due to falling stocks and became meaningless after 1918. In 1890 a hatchery for Schnäpel was put into operation in Bienenbüttel in Lower Saxony to support the stocks , without lasting success. The last sighting for the Weser comes from 1910, in the Elbe they have been considered extinct since 1935. In the catchment area of ​​the Ems and Eider, the last information comes from the 1970s.

The main reasons for the decline in the Danish population were: Destruction of the continuity of rivers due to the construction of weirs and dams and declining water quality, such as water pollution, silting up of spawning grounds of the gravel-spawning species, straightening of water bodies with the loss of connected quiet bays or floodplains, as habitat of the Fish larvae and fry. Pure restocking measures without reconstruction of the waters had remained completely unsuccessful, despite the population of millions. The species cannot negotiate weirs even when fish ladders have been installed. Today there are reproductive stocks in Denmark that are at least estimated to be more stable than those in Germany and the Netherlands, but it is not certain whether they would be able to survive without permanent stocking.

Species protection

Anadromous populations of the North Sea beak in the North Sea are listed by the European Union in Annex II and Annex IV of the Habitats Directive (FFH code: 1113). It is therefore a type of community interest , for the preservation of which the member states should designate special protected areas, but which are also strictly protected outside these areas. Since the species is largely believed to be extinct, this would not have any particular consequences. However, the statement is interpreted differently by conservationists. According to this view, protection includes all anadromous populations of Coregonus spp., Regardless of their current species status. The populations in the Baltic Sea, now mostly regarded as a separate species Coregonus maraena , are therefore classified as species in Appendix V, regardless of the species name to be used; it lists threatened species that are also used economically.

The Danish Coregonus population in the eastern North Sea, as the last surviving anadromous whitefish in the North Sea area, is today strictly protected in the European Union, attempts are being made to establish new populations in waters of the historical range where the species became extinct. In Germany, a larger project took place in Treene in Schleswig-Holstein . These animals are called Coregonus oxyrinchus , although the taxonomic problems are clear. However, this procedure has been officially agreed within the European Union.

Suspensions in the Rhine de Netherlands are mainly due to private initiative. For the Netherlands, due to the irreversible hydraulic engineering interventions, re-naturalization is assessed as hopeless.

As part of the migratory fish program NRW, Schnäpel were released from 1996 to 2006 in the Rhine near Rees and in the lower reaches of the Lippe . 2.3 million young North Sea billets with a mean of about 30 millimeters were released. The fish were bred in the Jäger-Kleinicke fish farm in Kiel . Adult fish were later caught in the release area. In 2014, North Sea bluebird larvae were detected for the first time and thus a successful reproduction of the released fish.

Taxonomy

The North Sea beak belongs to a species complex of closely related European species, the so-called lavaretus complex. The delimitation of species within the complex is problematic, the connection between morphologically and genetically delimited units within the aggregate is unclear. Since no genetic data is available for the North Sea beak, its true status can hardly be explained afterwards.

The species was first described by Carl von Linné in the tenth edition of his work Systema Naturae as Salmo oxyrinchus , the distribution is given as "in Oceano Atlantico". The spelling of the first description is binding for the name, so that later name variants (as linguistic emendations ) such as oxyrhinchos or oxyrhinchus are not permitted. Linnaeus' work builds heavily on that of his friend and colleague Peter Artedi , which he mostly follows in terms of content. He had described a "Coregonus maxilla superiore longiore conica" that occurs in "Flandria et Batavia", ie in Flanders and the mouth of the Rhine (where the historical Batavian tribe lived). Later authors have interpreted the Linnaeus name differently , depending on the concept used to structure the genus Coregonus , depending on the author, animals designated with this name are in the southern North Sea, in the North and Baltic Seas, or also in the waters of Scandinavia, and distributed in various inland lakes. The information in widespread field guides and identification works such as Vilcinskas or Muus and Dahlström are therefore unclear and refer to differently characterized and delimited units, which usually include several of the species that are differentiated today.

The species status of both historical and current populations has also been obscured by the displacement of animals outside their natural range through fishing stocking measures. Although two, rarely three, whitefish species occur naturally in the same body of water (syntopic), these are usually ecologically and morphologically clearly separated from one another. Species that are similar to one another naturally have vicarious distribution, so they only occur in clearly separated waters. Stocking with similar animals leads to the fact that species hybridize . In addition, populations, possibly supported by permanent stocking, are establishing themselves in waters where they were previously absent. In the Rhine, for example, vendace with short noses has been found in the Rhine, possibly for centuries, in addition to the North Sea beak, whose exact species association is unclear.

The Danish population is separated from the animals from the Baltic Sea using genetic markers; there is no evidence of current gene flow . However, the differences are extremely small. The researchers see the Danish North Sea population (for which they, together with the animals of the Baltic Sea, are reconstructing a glacial refuge at the mouth of the Elbe) as a separate ecotype rather than a separate species. Since no genetic data are available for the extinct Rhine population, these results cannot, however, be transferred to it. The Danish North Sea and Baltic Sea populations are morphologically differentiable on the basis of the gill spines, despite a certain overlap.

Individual evidence

  1. ↑ Overview "Fish of the Year" in Germany. German Fishing Association, accessed on February 26, 2018 .
  2. ↑ a b c d e J. Freyhof, C. Schöter (2005): The houting Coregonus oxyrinchus (L.) (Salmoniformes: Coregonidae), a globally extinct species from the North Sea basin. Journal of Fish Biology 67 (3); Pages 713-729. doi : 10.1111 / j.1095-8649.2005.00771.x
  3. ↑ a b Michael M. Hansen, Dylan J. Fraser, Thomas D. Als, Karen-Lise D. Mensberg (2008): Reproductive isolation, evolutionary distinctiveness and setting conservation priorities: The case of European lake whitefish and the endangered North Sea houting (Coregonus spp.). BMC Evolutionary Biology 8: 137. doi : 10.1186 / 1471-2148-8-137
  4. ↑ a b K. Østbye, L. Bernatchez, TF Næsje, K.-JM Himberg, K. Hindar (2005): Evolutionary history of the European whitefish Coregonus lavaretus (L.) species complex as inferred from mtDNA phylogeography and gill-raker numbers. Molecular Ecology 14: 4371-4387. doi : 10.1111 / j.1365-294X.2005.02737.x
  5. ^ A b c Jan Steinbring Jensen: The Houting Project. Urgent actions for the endangered houting Coregonus oxyrhynchus. Report, LIFE Nature-project LIFE05 NAT / DK000153 Urgent Actions for the Endangered Houting * Coregonus oxyrhynchus. edited by the Danish Ministry of the Environment, Nature Agency, 2013. ISBN 978-87-7279-690-1 . on this: Technical final report, covering the project activities from 02/01/2005 to 03/31/2013. July 2013
  6. ↑ a b c Christian Schröter: Revision of the beak and whitefish of the North Sea and south-western Baltic Sea area (Teleostei: Coregonidae). Diploma thesis, Rheinische Friedrich-Wilhelms-Universität Bonn, October 2002.
  7. ↑ Niels Jepsen, Michael Deacon, Anders Koed (2012): Decline of the North Sea houting: protective measures for an endangered anadromous fish. Endangered Species Research 16: 77-84. doi : 10.3354 / esr00386
  8. ↑ Lasse Fast Jensen, Dennis Søndergård Thomsen, Steffen S. Madsen, Mads Ejbye-Ernst, Søren Brandt Poulsen, Jon C. Svendsen (2015): Development of salinity tolerance in the endangered anadromous North Sea houting Coregonus oxyrinchus: implications for conservation measures. Endangered Species Research 28: 175-186. doi : 10.3354 / esr00692
  9. ^ Coregonus oxyrinchus in the IUCN Red List of Threatened Species 2015.4. Posted by: Freyhof, J. & Kottelat, M., 2008. Accessed March 1, 2016.
  10. ^ Jörg Freyhof & Emma Brooks: European Red List of Freshwater Fishes. published by the European Commission. Luxembourg: Publications Office of the European Union, 2011.
  11. ^ Anton Lelek & Günter Buhse: Fish of the Rhine, then and now. Springer-Verlag, 2013. ISBN 978 3 662 06645 4 , pages 86–87.
  12. ↑ Arno Waterstraat, Volker Wachlin, 2004: “Coregonus oxyrinchus (Linnaeus, 1758)” - North Sea bill . State Office for Environment, Nature Conservation and Geology Mecklenburg-Western Pomerania. PDF .
  13. ↑ BfN Federal Agency for Nature Conservation: Recording of migratory fish as part of the nationwide FFH monitoring. Method proposal, developed by experts from the federal state authorities and the BfN. Bonn, December 2011. PDF
  14. ^ SJ de Groot (2002): A review of the past and present status of anadromous fish species in the Netherlands: is restocking the Rhine feasible? Hydrobiologia 478: 205-218. doi : 10.1023 / A: 1021038916271
  15. ↑ Jost Borcherding: The North Sea Schnäpel is back in the Rhine. Nature in NRW 4/2014, pp. 32–36
  16. ^ Andreas Vilcinskas : Fish. Central European freshwater species and marine fish from the North and Baltic Seas. BLV, Munich 2000; P. 74. ISBN 3-405-15848-6 .
  17. ^ BJ Muus & P. ​​Dahlström: Freshwater fish in Europe. BLV Verlagsgesellschaft, Munich 6th edition 1990. ISBN 3-405-11867-0 , on page 72.
  18. ↑ Jan Dierking, Luke Phelps, Kim Praebel, Gesine Ramm, Enno Prigge, Jost Borcherding, Matthias Brunke, Christophe Eizaguirre: Anthropogenic hybridization between endangered migratory and commercially harvested stationary whitefish taxa (Coregonus spp.). In: Evolutionary Applications. 7, 2014, p. 1068, doi : 10.1111 / eva.12166 . PMC 4231596 (free full text)
  19. ↑ MN Hansen, KLD Mensberg, S. Berg (1999): Postglacial recolonization patterns and genetic relationships among whitefish (Coregonus sp.) Populations in Denmark, inferred from mitochondrial DNA and microsatellite markers. Molecular Ecology 8: 239-252.
  20. ^ Gesine Ramm & Jan Dierking (2014): North Sea and Baltic houting: gill raker morphometric differentiation between populations of the endangere fishes North Sea and Baltic houting. 18 pages download

Web links

Commons : Nordseeschnäpel ( Coregonus oxyrinchus )  - Collection of images, videos and audio files