Twaite shad (Alosa fallax)

Biology

Amphihaline species, schooling and strongly migratory at sea, pelagic with juveniles remain close to shore and estuaries; migrates from sea to rivers and spawns in main river often only few kilometers above limit or brackish water or in small rivers over gravel bottom; spawns in large, very noisy schools at night near the surface at midnight. Males migrate upriver at 2-3 years, females at 3-4; many individuals reproduce 3-4 seasons. Adults congregate near estuaries in April and enters rivers in May or early June when temperature reaches 10-12?C. Spawning takes place at night over sand or gravel, at a temperature range of 15-20?C. Adults return to sea after spawning, and could later return to spawn a second or third time. Eggs are demersal, scattered over gravel or sand; the fry move down river as they develop. Spent fish migrate back to the sea; most juveniles migrate to river mouth during first summer and move to sea at ed of second year where most remain until maturity. Individual fish apparently return to their natal spawning site. Ichthyophagous, feeds on small fishes and crustaceans, the young taking the fry of herrings, sprats and gobies. Adults do not feed when in freshwater. Sexually mature at an age of 3-4 years and a length of 30-40 cm. Suffers from river pollution and to some extent from river barrages. Very locally distributed due to pollution and impoundment of large rivers throughout Europe and most population declined during the first decade of the 20th century, but seem to have stabilized at a low level since the

Source: FishBase, licensed CC BY-NC 4.0.