Really not much too say on this piece as Salmon is probably the most recognisable fish in America when it comes too sushi. However, I suppose it would be worth noting that Salmon is not a traditional ingredient in sushi nor is it traditionally served raw/fresh.
Also, something that many of you might not know that the belly of the salmon contains a higher percent of fat in it. This cut is called Sake-Toro and has a bit more flavour than the rest of the body. Although this is something that's applicable too most or all larger fish; The cheeks and the collar or kama are the most tender; the stomach is fattier thus more flavourful; the back or the loin is more lean, thus more meatier; the tail is where all the tendons conjoin, thus the meat from the tail are usually scrapped off with a spoon, resulting in a mushy and rather unappetising mass of by-product.
Most American sushi cooks don't know about this part of the salmon as they usually discard most of the belly portion during the pre-prep of the salmon. Lazy bastards too lazy to maneuver their knife around the bones, just cut straight through it and off the entire piece.