Amaebi is a type of sweet shrimp prepared as sushi and sometimes sashimi. The shrimp are native to the Canadian Pacific ocean but they are found in the U.S. Pacific as well. The shrimp can be cooked but the cooked shrimp don't retain their sweet flavor.
Known as spot prawns in California they are typically seen whole in shell in Japanese restaurants. While typically served raw they are sometimes lightly steamed. The small prawns can also be added to paella as well as some soups and stews.
If you don't have Amaebi you can substitute: