| Habitat and Ecology: |
Habitat: Moderate to fast-flowing large to medium sized rivers with rock or gravel bottom. Spawns in fast-flowing water on shallow gravel beds often in small tributaries. May show a strong size related longitudinal distribution in smaller rivers, with adults inhabiting more upper river stretches.
Biology: Lives up to 12 years. Spawns for the first time at 4-5 years. May migrates some tens of km to spawning sites, which are often situated in tributaries, but which it does not inhabit in summer. Spawns in March-May when temperature reaches 12°C. Males form large aggregations, each male defending a small territory. Females spawn only once a year and, in some populations, during a very short period (3-5 days). Females deposit the sticky eggs into excavations made in gravel. Feeding larvae live along shores. Larvae live below surface. Early juveniles are benthic and inhabit very shallow shoreline habitats. When growing, they leave the shores for faster-flowing waters. Recruitment is closely related to high spring temperature, absence of spring floods and available shallow-water habitats along shores. Juveniles overwinter in backwaters or in cavities along shores. Adults form dense swarms during winter in lower parts of rivers. Larvae and early juveniles with superior mouth feed on small invertebrates. Larger juveniles and adults, which have inferior mouth, feed on benthic diatoms and detritus cleaned up from hard substrate in habitats with strong current.
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