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
Cisco (fish) Cisco (fish) The ciscoes (or "ciscos") are salmonid fish of the genus "Coregonus" that differ from other members of the genus in having upper and lower jaws of approximately equal length and high gill raker counts. These species have been the focus of much study recently, as researchers have sought to determine the relationships among species that appear to have evolved very recently. The term "cisco" is also specifically used of the North American species "Coregonus artedi", also known as lake herring. In previous taxonomic classifications, the ciscoes have been identified as a subgenus "Leucichthys" of the genus "Coregonus". Based