Common Roach
Rutilus rutilus
The common roach is a widespread freshwater fish belonging to the family Leuciscidae. It is characterized by a laterally compressed body, silvery scales, and a distinctive red iris. The species is highly adaptable and inhabits standing or slow-flowing waters across Europe and Western Asia. As a shoaling fish, it often forms large populations and serves as a fundamental food source for many predatory fish species.
Details
Identification
Red iris, silvery flanks, pelvic fins start vertically below the front edge of the dorsal fin.
Social behavior
Highly social shoaling fish, often forming mixed schools with other cyprinids such as bream.
Diet
Omnivorous; feeds on zooplankton, small crustaceans, insect larvae, algae, and aquatic plants.
Hunting strategy
Active foraging in the open water (pelagic) or on the water body floor (benthic).
Spawning substrate
Aquatic plants, roots, or stones in shallow shore areas (substrate spawner).
Overwintering
Retreats to deeper, low-current water areas and reduces metabolic rate.
Ecology
Ecological role
Important consumer in the aquatic food web and primary prey for predatory fish and waterfowl.
Natural predators
Northern pike, pike-perch, European perch, cormorant, grey heron, European otter.
Competitor species
Common bream, rudd, silver bream (competition for food and habitat).
Ecosystem service
Regulation of plankton and insect populations; basis for the fishery economy of predatory fish.
Threats
Habitat loss due to river engineering, severe eutrophication, and predation pressure from cormorants.
Scientific profile
Morphology & ID
Coloration
Back dark green to bluish, sides silvery, belly whitish. Characteristic red iris. Pelvic and anal fins are reddish to bright red.
Distinguishing features
Red iris; dorsal fin origin directly above or slightly behind the pelvic fin base; terminal mouth; pharyngeal teeth in a single row (usually 5-5 or 6-5).
Confusion species
Rudd (Scardinius erythrophthalmus) - has superior mouth and dorsal fin clearly behind pelvic fin base; Ide (Leuciscus idus) - has smaller scales; Common dace (Leuciscus leuciscus).
Sexual dimorphism
Males develop a fine-grained spawning rash (nuptial tubercles) on the head and body during the breeding season.
Habitat
Fish region
Bream zone (metapotamal), but occurs eurytopically in almost all water types.
Preferred zone
Littoral zone of standing waters and slow-flowing sections of rivers.
Flow preference
Eurytopic, prefers standing to slow-flowing waters (stagnophilous to indifferent rheotype).
Substrate preference
Sand, gravel, but also muddy substrate with macrophyte growth.
Oxygen requirement
Moderate; tolerant of temporary oxygen depletion.
Migration
Migration behaviour
Short-distance migrations to spawning grounds in shallow littoral areas or tributaries.