Salmon roe was originally consumed in Japan in a preparation called sujiko. Initially, the roes are not individually separated and remain bunched in a thin transparent membrane. This casing of salmon roe is usually salted or immersed in soy sauce for a period of time. As a result the roe becomes less turgid due to water loss, and has a very strong and concentrated taste, along with a sticky texture compared to ikura.
Originally, the roes were prepared from Pacific salmon species. Recently, there are Atlantic salmon being used for sushi as well, and they have slightly smaller roes. The Atlantic roes have a lighter taste, and don’t have a strong aroma to them, which some people may prefer. The Pacific roes are bigger and have a strong accent of salmon flavor with them.