Biology

Found in clear and moderately swift flowing water, with a substrate of sand and pebbles. Prefers to inhabit middle stretches of the main branches of rivers and streams, sometime the lower stretches. Also occurs in very short coastal streams (less than 5 km) and usually has not been encountered in intermediate size streams (5-35 km). Moves to the sea or the lower stretches of streams and rivers after spawning, where it stays until about April-May, when temperatures of the water start to rise. Possibly does not go far into the sea, but may stay in river mouths or at sea close to river mouths during winter. Spawns in October-November. Migrates upstreams in small groups of more than 10 individuals and probably comes back after breeding (Ref. 83424).