Tench
Tinca tinca
The tench is a robust freshwater fish characterized by its very small scales and an extremely thick, protective mucus layer. It prefers stagnant or slow-moving waters with muddy bottoms and dense aquatic vegetation. The species is well-known for its extraordinary resilience to low oxygen levels and acidic environments. During winter, it often enters a state of dormancy, spending the time buried deep within the mud.
Details
Identification
Very small cycloid scales, reddish iris, two short barbels, rounded fin edges, deep green to golden-brown coloration.
Social behavior
Solitary or living in small groups; usually hidden in vegetation during the day.
Diet
Diet consists of insect larvae, snails, mussels, and small crustaceans rooted out from the mud.
Hunting strategy
Bottom-rooting in the mud (suction-feeding mechanism) to ingest benthic organisms.
Spawning substrate
Fine-leaved aquatic plants (phytophilous spawner).
Overwintering
Dormancy buried in the mud.
Ecology
Ecological role
Important consumer in the benthic food web and prey for large predatory fish.
Natural predators
Pike, catfish, European otter, cormorant, grey heron.
Competitor species
Carp and bream (food competition in the benthic zone).
Ecosystem service
Economically significant in aquaculture and as a popular target for recreational fishing.
Threats
Loss of shallow water zones due to bank stabilization and drainage of wetlands.
Scientific profile
Morphology & ID
Coloration
Dark green to olive-brown with a golden sheen; yellowish belly; conspicuous orange-red iris.
Distinguishing features
Very small scales (90-115 along the lateral line), one pair of short barbels at the mouth corners, all fins strongly rounded.
Confusion species
Crucian carp (Carassius carassius) - lacks barbels; Prussian carp (Carassius gibelio) - lacks barbels and has larger scales.
Sexual dimorphism
Males have significantly larger, spoon-shaped pelvic fins with a thickened second ray; females have smaller, more pointed pelvic fins.
Habitat
Fish region
Bream zone as well as standing waters (lakes, ponds, oxbows).
Preferred zone
Benthic (bottom area) in the littoral (shore zone) with dense submerged vegetation.
Flow preference
Limnophilous; prefers standing to very slow-moving waters.
Substrate preference
Fine-grained, muddy substrates with a high proportion of organic detritus.
Oxygen requirement
Very low; can tolerate extremely low oxygen levels through emergency respiration and metabolic adaptation.
Migration
Migration behaviour
Potamodromous; performs short migrations between deep wintering sites and shallow, vegetation-rich spawning grounds.
Reproduction
Spawning substrate
Phytophil; Eier werden an feinblättrigen Wasserpflanzen (z.B. Myriophyllum, Elodea) abgelegt.