Red American marsh crayfish
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Red American crayfish ( Procambarus clarkii ) |
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| ( Girard , 1852) |
The Louisiana crayfish or Red American crayfish ( Procambarus clarkii ), also Louisiana crayfish , is a species of North American crayfish. It is native to the southeastern United States and northern Mexico , the Gulf of Mexico and the Mississippi lowlands (north to Illinois ), particularly common in Louisiana .
Appearance
Procambarus clarkii grows up to 12 cm, but occasionally specimens can reach a length of 15 cm. Its body is thorny and dark red to black (sometimes gray or greenish); the claws are studded with bright red thorns. It only has a post-orbital bar. Males can be distinguished from females by the gonopodia and the larger claws.
habitat
The red marsh crayfish prefers stagnant water, which is regularly dry part of the year. In the natural habitat, these are flood pools in river plains . Introduced today, the species is very common in rice fields that resemble the natural habitat. The species is very adaptable to the extreme conditions in the strongly heated waters of its warm-temperate to subtropical habitat. It is able to live permanently in water with an oxygen content of 2 mg / l and can also survive lower levels or anaerobic conditions for some time. Procambarus clarkii can tolerate certain salinity in its living waters.
Procambarus clarkii is (like almost all crayfish species) nocturnal. Cancer avoids the dehydration of its living waters by digging earth tubes that are created above the water level when the water level falls. The species is able to survive regular periods of drought of six months without damage. It is also able to actively leave bodies of water by land.
Due to its importance for edible crab production, cancer has been bred in many places around the world and has often escaped from culture and into freedom. Further settlements go back to aquarists who, unaware of the problems and damage involved, exposed the species or kept it in garden ponds.
nutrition
Like most crayfish species, the American red crayfish is omnivorous in the diet . As a herbivore it can feed on marsh and aquatic plants, this diet is the most important in cancer breeding. In addition, it feeds on animal prey as a predator, preferably on soft-skinned mosquito larvae and thin-shelled water snail species . It can also prey on fish spawn and tadpoles . In addition, you can only eat with dead plant material, rotted leaves or bacteria-rich mud.
The foraging of American red crayfish can have a very strong impact on inhabited waters (key ecological species). In Spain, clear lakes rich in aquatic plants have been converted to cloudy, plant-free waters after the introduction of the species. Even as a predator, it influences the community in the populated waters because it can reach very high population densities. The species also feeds cannibally on younger conspecifics.
As studies on Lake Naivasha in Kenya show, the red American marsh crayfish is also able to tap terrestrial sources of food. Small crayfish populations, which spent the day buried in the water-filled footsteps of hippos , left their hiding place at night and ate on land plants.
Growth, life cycle
In the wild, the species usually reaches an age of two years in its native North America . Investigations in European waters indicate that on average it is getting a bit bigger and older here, in Italian investigations an average age of five years was reached. This can probably be explained by the less favorable living conditions for reproduction. In the aquarium (like most animal species in captivity) the species can reach a slightly older age.
As is typical for crayfish, the red American marsh crayfish does not lay its eggs either; these are carried by the female on the abdomen under the folded tail fan. Usually the first two stages also remain on the mother animal after hatching (usually buried in the ground in the field because egg-bearing females cannot use their tails as usual to escape).
Like all other cancers, the American red marsh crab must molt to grow. The molt is a dangerous endeavor for any cancer, and it can die at any time if it gets stuck in the shell. The pet owner can tell his cancer a few days in advance that it will molt. A sign of this is that from now on he hides more and eats less so that he can draw the nutrients from his old shell and since his skeleton becomes soft. The next step is for the armor to pop open between the head-chest piece and the abdomen. Then the crab pumps water into the shell and blows it open. He strips off the armor with rhythmic blows with his tail. The new shell is still very soft for the first few days after molting. One then speaks of the so-called "butter crab".
The species grows with each molt until sexual maturity is reached, then no longer. Usually about ten molting is required to reach maturity. Under favorable conditions, the animals become sexually mature after about six months. Reproduction can take place in the open under favorable conditions at any time (even several times a year), mostly due to the environmental conditions a maximum can be observed in autumn.
use
Procambarus clarkii is by far the most widely bred freshwater crab in the world. If you buy unspecified "crayfish" meat in the supermarket, it is almost certainly of this type. In 2007 world production exceeded 300,000 t. For several years the world's most important producer has been China, to which the species was introduced. The population now exceeds that in his native North America. There, too (especially in Louisiana), cancer breeding is of great economic importance. The only notable European producer is Spain with approx. 2,000–3,000 t. In Germany, the species is not bred commercially (mainly because of its heat requirements). The crabs are mostly kept in specially created crayfish ponds, there are also farms in rice fields as a secondary use. Other rice growers fight the species as a pest, mainly because of its burrowing activity.
According to press reports, a Berlin fishing company has applied for and received permission to catch the red American crayfish in two Berlin waters, in the Tiergarten and Britzer Garten , where the species, presumably released by aquarists, has been naturalized and is now occurring in large numbers. Previously, attempts had been unsuccessful to reduce the stock by fishing without exploitation. In 2018, 39,000 crabs were caught in this way.
In addition, it was traditionally one of the most popular crabs among aquarium keepers, sometimes also in garden ponds. Orange or blue colored cultivars are particularly popular in keeping. In a study in the Czech Republic, it was the third most popular crayfish species with around 20 percent.
Ecological problems
The swamp crayfish is one of the problematic neozoa worldwide . In North America, too, it has been introduced into numerous areas outside its natural range, where it threatens endemic cancers, which are much more numerous in North America than on the European continent.
In other parts of the world, including Europe, it is, like all North Americans, a danger as a carrier of cancer plague . This infectious disease is mild in himself, but is fatal for exposed European, African and Australian species. In waters where North American crayfish species have been established, all native species will inevitably die out.
The red marsh crayfish has a high potential to spread due to its modesty. In Spain, where it was released in 1973, it has severely decimated some amphibian species through direct predation and changes in habitat . Today it can also be found in some places in Germany and Switzerland and currently seems to be spreading northwards. In 2014, several specimens were discovered in an outdoor swimming pool in Frankfurt am Main . In the summer of 2017, the red crabs also caused a sensation in Berlin near the Tiergarten when they set out from their residential tunnels on the swampy banks to colonize other areas when the water levels rose after the rainy period. The animals have also been in Offenbach am Main since 2017 , where they are sometimes fought with eels as predators. It is also fished in the Britzer Garden in Berlin.
American red crayfish was added to the EU 's list of invasive alien species of Union concern in 2016.
Keeping in the aquarium
The red marsh crayfish has traditionally been popular with aquarists. The brightly colored animals, which are also active during the day, are considered attractive, even if there have always been problems with eating water plants and preying on fish and other invertebrates such as water snails. The species was widely traded online, in isolated cases to this day. With the legal force of the ordinance on the prevention and management of the introduction and spread of invasive alien species of October 22, 2014 (see list of invasive alien species of Union-wide importance ), however, not only the release into the environment, but also breeding and trade with the red American marsh crayfish is prohibited in principle in the European Union. Non-commercial owners, such as private aquarists, are allowed to keep the animals until the end of their natural lifespan, but not to breed and multiply them. All transition periods for commercial trade have now expired.
literature
- C. Chucholl, P. Dehus: Crayfish in Baden-Württemberg . Fisheries Research Center Baden-Württemberg (FFS), Langenargen 2011.
- Hans Gonella: Crabs, crabs and prawns in the freshwater aquarium. Bede, 1999, ISBN 3-931792-87-0 .
- W. Ray McClain, Robert P. Romaire: Procambarid Crayfish: Life History and Biology. (= SRAC Southern Regional Aquaculture Center Publication. No. 2403). 2007.
- Crawfish Production Manual. (= LSU Ag. Center Publication. No. 2637). Louisiana State University.
- Silvia Barbaresi, Francesca Gherardi: The invasion of the alien crayfish Procambarus clarkii in Europe, with particular reference to Italy. In: Biological Invasions. 2, 2000, pp. 259-264.
- Barbara Renai, Francesca Gherardi: Predatory efficiency of crayfish: comparison between indigenous and non-indigenous species. In: Biological Invasions. 6, 2004, pp. 89-99.
Web links
- Online identification key for crayfish in Baden-Württemberg
- Procambarus clarkii inthe IUCN 2013 Red List of Threatened Species . Posted by: Crandall, KA, 2010.
Individual evidence
- ↑ a b Kathrin Zinkant: In Berlin, crabs are now crawling over the asphalt . Southgerman newspaper. August 23, 2017. Retrieved August 23, 2017.
- ↑ J. Gray, MC Jackson: Leaves and Eats Shoots: Direct Terrestrial Feeding Can Supplement Invasive Red Swamp Crayfish in Times of Need. In: PLoS ONE . 7 (8), 2012, p. E42575. doi: 10.1371 / journal.pone.0042575
- ↑ Will the Berlin marsh crabs end up on dinner plates soon? Article, Die Welt online Wissen, May 6, 2018.
- ↑ There are fewer marsh crabs in Berlin
- ↑ J. Patoka, M. Petrtýl, L. Kalous (2014): Garden ponds as potential introduction pathway of ornamental crayfish. Knowledge and Management of Aquatic Ecosystems (2014) 414, 13. doi: 10.1051 / kmae / 2014019
- ↑ Chucholl, C. & Blank, S. & Brinker, A. (2017): The protection of the crayfish - A guide . Ministry for Rural Areas and Consumer Protection Baden-Württemberg, Stuttgart, 84 pages
- ↑ Berlin-Tiergarten: Yes, you see correctly! Cancer walk in front of the Spanish embassy. In: BZ , August 17, 2017, accessed on August 18, 2017.
- ↑ After 1000 eels were released: The number of unwanted crabs in the Schultheisweiher is falling In: OP-online.de, July 20, 2018, accessed on May 13, 2019
- ↑ In Offenbach, the appearance of the American marsh crabs is causing great concern.In : echo-online.de, August 24, 2017, accessed on May 13, 2019
- ↑ https://gruen-berlin.de/nachricht/fischreusen-im-britzer-garten
- ↑ List of Invasive Alien Species of Union Concern (PDF) accessed on May 15, 2016.
- ↑ Christoph Chucholl (2013): Invaders for sale: trade and determinants of introduction of ornamental freshwater crayfish. Biological Invasions 15 (1): 125-141. doi: 10.1007 / s10530-012-0273-2
- ↑ Giuseppe Mazza, Laura Aquiloni, Alberto Francesco Inghilesi, Claudia Giuliani, Lorenzo Lazzaro, Giulio Ferretti, Lorenzo Lastrucci, Bruno Foggi, Elena Tricarico (2015): Aliens just a click away: the online aquarium trade in Italy. Management of Biological Invasions 6 (3): 253-261. doi: 10.3391 / mbi.2015.6.3.04
- ↑ Stefan Nehring: The invasive alien species of the first Union list of the EU regulation No. 1143/2014. BfN-Skripten 438, 2016. published by BfN, Federal Agency for Nature Conservation, Bonn. ISBN 978-3-89624-174-0