Bitterling (fish species)
Bitterling ( Rhodeus amarus )
|( Bloch , 1782)|
The bitterling ( Rhodeus amarus , Syn . : Rhodeus sericeus amarus Pallas, 1776) is a carp fish (Cyprinidae). It can be found in plant-rich, shallow, slow-flowing or stagnant waters with sandy or muddy bottoms. The bitterlings are dependent on mussels for reproduction , which inhabit the same habitat. The 6 to 9 cm large fish feed on invertebrates and algae of the plankton . Their distribution area is in Central Europe north of the Alps , west to the Rhone region , east to the Caspian Sea . However, they are absent in Scandinavia , Denmark and much of the UK . The bitterling was named "Fish of the Year" in Germany in 1985 and 2008 and in Austria in 2008. The bitterling is also found in Teufelssee in Berlin-Grunewald .
The bitterling is a small species of fish with a relatively high back and a half-set mouth. The body is protected by large scales, the pores of the incomplete side line are only visible on the first 4 to 7 scales behind the head. Most of the year the back is gray-green in color, the sides and belly are silvery. An opalescent stripe of blue-green color runs across the middle of the pages. During the spawning season, the colors of the males intensify - throat, chest and front side of the abdomen become reddish, the back and rear body shimmer green. Spawning warts appear in two places above the eyes and the mouth and a bruise behind the gill covers.
The spawning season takes place between April and June, depending on the water temperature. During this time, the females grow a 5 to 6 cm long laying tube behind the anal opening. This helps the female to lay the eggs (per female a total of 40 to 100 pieces with a diameter of up to 3 mm) in the gill space of large freshwater mussels, whereby each mussel only receives one or two eggs. The intensely marked Milchner show a pronounced territorial behavior towards their rivals. However, the aggression at the beginning of the territorial formation decreases as soon as the Rogner has laid his eggs. The males' sperm pass through the breath water into the gill space of the mussels and fertilize the eggs there. Until the larvae can swim, they remain - largely protected from enemies - in the mussels. The mussels benefit from the fish in that their larvae ( glochidia ) attach to them and are spread through them.
Bitterlings mostly live in river underflows, old river arms and some lakes, where they visit bays with a muddy bottom where the great river mussel ( Unio tumidus ) or the great pond mussel ( Anodonta cygnea ) occur. The males choose a shell in spring and initially drive away the females from it. The presence of mussels only triggers the change of color to the “wedding dress” and courtship behavior in the male. When a sexually mature female approaches, they begin to lure her to her mussel in a complicated ritual. Finally the female pushes the laying tube into the gill space of the mussel and lays her eggs there. The male drains his seminal fluid ("milk") through the mollusc's intake opening, which reaches the roe with the water .
The fertilized eggs develop inside the mussel and the small bitterlings leave them after two to four weeks. The male even occasionally lures several females to his mussel. The same mussel is sometimes used by other pairs of bitterlings, so that over 100 different stages of development of the young bitterlings can be counted in it. The four to five years old fish reach sexual maturity in the second year of life.
Hazard and protection
The International Union for Conservation of Nature ( IUCN) lists the bitterling in the Red List of Endangered Species as Least Concern . However, local threats from water pollution, weed removal and stocking with predatory fish are cited.
Due to its special reproductive biology, i.e. the dependence on the simultaneous occurrence of certain types of mussels, the bitterling has become an endangered fish species in some regions of Central Europe. Due to water pollution and maintenance measures (dredging, etc.), the populations of these mussels have declined or even eradicated in many places.
Red list classifications in Europe
- Red List Federal Republic of Germany: 2 - highly endangered
- Austria's red list: 3 - endangered
- Red list of Switzerland: EN (corresponds to: highly endangered)
Legal protection status in Europe
- Fauna-Flora-Habitat-Guideline (FFH-RL): Annex II (special protected areas are to be designated)
The Bitterling was voted " Fish of the Year 2008" by the Association of German Sport Fishermen (VDSF) and the Austrian Board of Trustees for Fisheries and Water Protection (ÖKF) . The Association of German Sports Divers (VDST) and the Federal Agency for Nature Conservation (BfN) joined the election for the first time .
- Günther Sterba : The world's freshwater fish. 2nd Edition. Urania, Leipzig / Jena / Berlin 1990, ISBN 3-332-00109-4 .
- Overview "Fish of the Year" in Germany. German Fishing Association, accessed on February 26, 2018 .
- Overview "Fish of the Year" in Austria. Austrian Board of Trustees for Fisheries and Water Protection, accessed on February 26, 2018 .
- Tolerated rivals. The mating systems that can be observed in the animal kingdom are characterized by spending energy, time and food only on their own offspring. For the males, this often means having to defend their own females against competitors. As British researchers have now found on the basis of the mating behavior and the defense of the territory in freshwater fish, it can also make sense for males to tolerate rivals to a certain extent.
- Rhodeus amarus in the Red List of Threatened Species of the IUCN 2009. Posted by: Freyhof, J. & Kottelat, M., 2008. Accessed March 7, 2010.
- Bitterling (fish species) on Fishbase.org (English)
- Bitterling on www.pivi.de
- Pictures and videos at fischbottich.de
- On the ecology of stickleback ( Gasterosteus aculeatus L.), bitterling ( Rhodeus sericens amarus Bloch, 1782) and Moderlieschen ( Leucaspius delineatus Heckei, 1843) - three endangered, indigenous small fish species.