Sushi is commonly eaten with condiments. Sushi may be dipped in shoyu, soy sauce, and may be flavored with wasabi, a piquant paste made from the grated root of the Wasabia japonica plant.
True wasabi has anti-microbial properties and may reduce the risk of food poisoning. The traditional grating tool for wasabi is a sharkskin grater or samegawa oroshi. An imitation wasabi (seiyo-wasabi), made from horseradish, mustard powder and green dye is common. It is found at lower-end kaiten zushi restaurants, in bento box sushi and at most restaurants outside of Japan. If manufactured in Japan, it may be labelled "Japanese Horseradish".
During a salmon run, bears will only eat the skin and discard the rest of the fish. This is because the layer just below the skin is the fattiest. Salmon skin isn't like chicken skin, it contains lots of good fat, omega 3 fatty acids. So, yes it is healthy to eat. Bears, wolves, eagles, seagulls ( when the salmon are young ), orcas, and other fish. Also humans eat a lot of salmon.
One fascinating new area of health benefits involves the protein and amino acid content of salmon. Several recent studies have found that salmon contains small bioactive protein molecules (called bioactive peptides) that may provide special support for joint cartilage, insulin effectiveness, and control of inflammation in the digestive tract.