Twait shad Twait shad The twait shad or twaite shad ("Alosa fallax") is a species of fish in the family Clupeidae. It is found in the eastern Atlantic Ocean and the Mediterranean Sea and is an anadromous fish which lives in the sea but migrates into fresh water to spawn. In appearance it resembles an Atlantic herring but has a row of six to ten distinctive spots on its silvery flanks. They become mature when three or more years old and migrate to estuaries, later swimming up rivers to spawn. Populations of this fish have declined due to overfishing, pollution and habitat
Herring as food in Europe, and early in the twentieth century their study was fundamental to evolution of fisheries science. These oily fish also have a long history as an important food fish, and are often salted, smoked, or pickled. Herring are very high in the long-chain Omega-3 fatty acids EPA and DHA. They are a source of vitamin D. Water pollution influences the amount of herring that may be safely consumed. For example, large Baltic herring slightly exceeds recommended limits with respect to PCB and dioxin, although some sources point out that cancer-reducing effect of omega-3 fatty acids is statistically stronger than