Salmon roe. イクラ。
The term is a loan word from the Russian ikra, caviar. Although not as precious as its Russian namesake, the large, bead-like ikura-spheres have a beautiful orange color and taste deliciously. Ikura is popular sushi topping and is also used in chirashi-zushi and onigiri. It is also used as a topping for donburi.
By the way, salmon roe "in the sac" is called sujiko and is preserved with salt. It can also be pickled with sakekasu. Compared to ikura, sujiko is dark-red and it tastes sweeter.
[Ikura]