Common Nase
Chondrostoma nasus
The Common Nase is a rheophilic freshwater fish of the cyprinid family, featuring a spindle-shaped body and silvery flanks. It is characterized by its distinctive undershot, transverse mouth with a hard, horny edge used for scraping algae from submerged stones. It typically inhabits the grayling and barbel zones of medium to large rivers with gravelly substrates and clean water.
Details
Identification
Nose-like protrusion above the mouth; mouth opening straight and transverse; horny lower lip; back grey-blue, belly whitish, fins (except dorsal) often reddish.
Social behavior
Highly gregarious; forms large schools, especially during feeding and spawning migrations.
Diet
Specialized algae eater; scrapes periphyton (diatoms) from stones, also consuming small invertebrates living within the algal mats.
Hunting strategy
Actively grazes on algal mats at the river bottom, often showing flashes of their silver bellies as they turn sideways to scrape.
Spawning substrate
Loose gravel and stony substrate in shallow, fast-flowing river sections.
Overwintering
Withdraws to deeper, calmer river sections or downstream areas during the winter months.
Ecology
Ecological role
Important primary consumer converting algal biomass into animal biomass; serves as prey for large predators like huchen and pike.
Natural predators
Huchen, Northern pike, Great cormorant, Common merganser, Eurasian otter.
Competitor species
Other rheophilic cyprinids such as barbel or Danube roach (partial habitat overlap).
Ecosystem service
Regulates algal growth on river substrates; contributes to nutrient transport through migration.
Threats
River engineering and damming (interruption of migration routes), loss of spawning habitats due to sedimentation, predation pressure.
Scientific profile
Morphology & ID
Coloration
The back is dark grey to olive green, the sides are silvery. The belly is whitish. Pectoral, pelvic, and anal fins often show a reddish tint, while the dorsal and caudal fins are typically dark grey.
Distinguishing features
Characteristic transverse, subterminal mouth with sharp, horny lips (scraping mouth). The snout is thick and protrudes over the mouth like a nose, giving the species its name.
Confusion species
Vimba bream (Vimba vimba), Common dace (Leuciscus leuciscus), Common barbel (Barbus barbus). The Vimba bream has a significantly longer anal fin, the dace has a terminal mouth.
Sexual dimorphism
During the spawning season, males develop a very distinct, fine-grained spawning rash (tubercles) over the entire head and back.
Habitat
Fish region
Barbel zone (Epipotamal)
Preferred zone
Benthic (bottom-oriented)
Flow preference
Strongly rheophilic; prefers fast-flowing, turbulent river sections.
Substrate preference
Gravelly to stony (Lithophilic); requires hard substrates for feeding (algal periphyton).
Oxygen requirement
High; the species is sensitive to oxygen depletion, typically requiring > 7 mg/L.
Migration
Migration behaviour
Distinct spawning migrations upstream to suitable gravel beds in tributaries or upper reaches, often covering distances from 10 to over 100 km.
Reproduction
Spawning substrate
Coarse gravel and stones in shallow, fast-flowing areas (Lithophilic).
Larval phase
After hatching, larvae remain in the gravel interstitial; after emergence, they drift into calm, shallow shoreline areas (nurseries).
Parental care
None; eggs are deposited in pits within the gravel and are not guarded.
Diet
Feeding type
Herbivorous and detritivorous; specialized algae eater.
Diet juvenile
Zooplankton, small insect larvae (chironomids), and diatoms.
Diet adult
Primarily periphyton (algae) scraped from stones with horny lips; small benthic invertebrates are also consumed in the process.
Feeding strategy
Grazer; uses the specialized scraping mouth to exploit algal films on hard substrates.
Schooling
Strong schooling behavior throughout the entire life cycle, especially during migrations and feeding.
Ecological role
Role in food web
Primary consumer; converts algal biomass into fish biomass and serves as important prey for predatory fish (Huchen, Pike) and birds.
Natural predators
Danube salmon, Northern pike, Wels catfish, Great cormorant, Common merganser.
Competitor species
Other rheophilic cyprinids like the common barbel (Barbus barbus) regarding spawning grounds and habitat.
Parasites
Commonly infested by trematodes (e.g., Posthodiplostomum cuticola) and parasitic crustaceans.
Bioindicator function
Key species of the barbel zone; indicator for good water quality and the ecological connectivity of river systems.
Fisheries & legal
Fishing regulation
Protected year-round in many German federal states or protected by high minimum sizes and long closed seasons.
Closed season
Varies regionally, usually March 1st to May 31st (spawning season).
Economic use
Historically an important food fish, today economically insignificant but ecologically and recreationally valuable.
Protection & threats
Main threats
Fragmentation of migration routes by dams/weirs, loss of gravel spawning grounds due to sedimentation and impoundment, predation in weakened populations.
Population trend
Locally stabilizing in many large rivers (Rhine, Danube, Elbe) following dramatic declines in the 20th century due to stocking and restoration, but remains threatened.
Conservation measures
Restoration of river connectivity (fish passes), vitalization of gravel beds, removal of bank reinforcements, targeted stocking programs.