Alosa to detect ultrasound (at frequencies above 20 kHz, which is the limit of human hearing). This was first discovered by fisheries biologists studying a type of shad known as blueback herring, and was later verified in laboratory studies of hearing in American shad. This ability is thought to help them avoid dolphins that find prey using echolocation. "Alosa" species are generally pelagic. They are mostly anadromous or semianadromous with the exception of strictly freshwater landlocked species. "Alosa" species are generally migratory and schooling fish. Males usually mature about a year before females; they spawn in the late spring to summer.
Ide (fish) the wild in at least one site within New Zealand. Ide occurs in schools in the clear pools of larger rivers, ponds, and lakes but they may move to deeper waters during the winter before moving into shallow freshwater to spawn in the spring. The species is also found in the Baltic Sea, which has a lower salinity than most seas and in Sweden the fish spent the first year of their lives in rivers before joining the more mature fish as they migrated downstream into the Baltic Sea during the summer months. The fish then returned to the rivers