Kazunoko (数の子), or herring roe, are tiny fish eggs in their enclosing skein. This caviar is a popular delicacy for Japanese New Year’s Feast (Osechi Ryori). Since kazunoko, or fish roe, represents eggs and fertility, eating kazunoko is said to bring prosperity of many children and as a prayer for healthy children. It is typically prepared by removing the salt for a day before lightly seasoned in a dashi broth.
In the US, you can find kazunoko at Japanese grocers like Nijiya at the end of December. You can also find it from online seafood supplier store.