The main fish used in a California sushi roll is imitation crab meat. While it is called crab, it is not actually made from real crab meat but is instead made from a combination of fish, usually pollock, that is then flavored and textured to resemble crab meat. This was invented in the 1970s in California as a way to present sushi to customers who were not used to raw fish. Other ingredients in a California sushi roll typically include avocado, cucumber, and sometimes tobiko (flying fish roe) or sesame seeds.