Twait shad are silvery, sometimes with a bronzy tinge, and there are a distinctive row of six to ten large dark spot just behind the gill cover though these may fade when the fish is dead. The adult length is typically . The twait shad is found in most of Europe and all countries bordering the Mediterranean Sea. "Alosa fallax" has a similar lifecycle to "A. alosa" (allis shad). They are known to live in sympatry. Some studies have suggested "A. fallax" and "A. alosa" species can hybridize. They are anadromous species, like many other species in the genus "Alosa". However, some
Mattapoisett River mill purposes" and featured three herring weirs; the "Upper Herring Weir" in Rochester, the "Middle Weir" or "Church's Weir", and the "Lower Herring Weir" at the entrance to Mattapoisett Harbor. Fish populations drastically declined during the twentieth century until they were almost extinguished, but local restoration efforts from the 1980s onwards have fostered a slow recovery. The principal restoration tactic has been to remove snags and other obstacles from the river that serve to impede fish migrations. The Lower Herring Weir is one of the few rivers emptying into Buzzards Bay that has electronic fish counters installed. Reports from Alewives