Answer 1:
In Japanese cuisine, a variety of fish roe are utilized; the name “caviar” can be misleading since some people believe it solely refers to sturgeon roe, but in current times, many people use the phrase to refer to a variety of fish roe. This is significant since sturgeon caviar is rarely used in sushi.
What you will notice are
Ikura is an orange-red salmon roe with a diameter of 2 to 6 mm that is sometimes used in hand rolls but is most commonly presented in the “boat” type of nigiri sushi. Ikura is a Japanese borrowed word for caviar derived from the Russian term.
Tobiko is a tiny (0.5 to 0.8 mm) flying fish roe that is naturally reddish-orange in color with an unique crunchy feel. It is occasionally served with other foods to modify its color to yellow, green, or black. It’s sometimes used in nigiri sushi boats, but it’s most recognized for its use in maki sushi, notably the California roll.
Masago is smelt or capelin roe that is even smaller and less crunchy than tobiko but serves the same purpose.
Uni – sea urchin roe (eating the entire reproductive organ, not just the eggs) is exclusively used in nigiri sushi; I’ve never seen it in rolls.
In addition to sushi, all of these fish roes, as well as a few others, are utilized in a range of Japanese cuisine dishes.
Answer 2:
Salmon roes (Ikura) and Tobiuo roes are the only two options (Tobito).
Western caviar (Sturgeon) is not used by old school sushi chefs because it is a Western gourmet element.
However, in recent years, several more upscale sushi restaurants have begun to include Western caviar in their menus (but actually not eaten with sushis, but used in seperated dished)
