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.
Soused herring process of preparing herring (known as "gibbing") was developed in the Middle Ages by the Dutch. Herrings are caught between the end of May and the beginning of July in the North Sea near Denmark or Norway, before the breeding season starts. This is because herrings at this time are unusually rich in oils (over 15%) and their roe and milt have not started to develop. The brine used for Dutch soused herring has a much lower salt content and is much milder in taste than the German Loggermatjes. To protect against infection by nematodes of the genus Anisakis, European