Sushi refers not to the fish but to rice seasoned with rice wine vinegar, sugar and salt. In fact, it wasn’t until the late 1820’s that sushi and raw fish were first combined to create an inexpensive food for busy streets and known as Edo (former name for Tokyo) style sushi.
The earliest reference to sushi dates back to 718, when it was introduced to Japan as a fermentation of fish with rice, due to the lack of refrigeration; the origin of sushi though seems to be southeast Asia. A few hundred years later, sushi has evolved to the point where the fermentation process has been abandoned and vinegar is substituted.
Sushi has since become popular around the world and is the ultimate fast food that can be eaten with chopsticks or fingers.
Sushi is very low in fat and very nutritious. The fish often used are tuna and salmon both of which are high in Omega-3. Seaweed is rich in iodine and rice provides complex carbohydrates.
Like many cuisines, sushi is an evolving one. When it was first taken to America, the chefs there made famous the California Roll which was created to introduce sushi to the Western palette.