There's actually no such fish as a sardine. "Sardine" is a term that refers to various kinds of small fish that have been processed and canned. The name derives from the Mediterranean island Sardinia. Sardines from Denmark and Norway are usually brisling and silds. Those from Maine are small herrings, and those from France, Portugal and Spain are pilchards, a smaller and fatter variety of herring.
Nor is there a fish called a scrod. The name comes from a Middle Dutch word, "schrode," meaning a strip or shred. In New England, scrod are immature cod or haddock weighing a pound or two. And Atlantic salmon isn't really a salmon at all—it's actually a member of the genus Salmo, or trout family. The misnomer is so widely accepted that it would only cause confusion to rename the species.