Meaning
筋子 (すじこ, Sujiko) is Sujiko, a Japanese food (fish eggs).
What is Sujiko?
Sujiko is, like ikura , salmon roe. The difference is that sujiko is still inside its membrane when it is prepared. It also has a different color: sujiko is red to dark-red while ikura is lighter in color, sometimes almost orange. Sujiko is also sweeter in taste.