When people talk about ..., the first ~ they think of is ~.
ーWhen you think of Japan, you think of Samurai.
「日本といえば、侍だよね」
When you think of ..., you think of ~. で「…と言えば、〜だよね」と表現できます。
ーWhen people talk about Sushi, the first fish they think of is Maguro/Tuna.
「寿司と言えば、マグロだよね」
When people talk about ..., the first ~ they think of is ~.「…について話すとき、最初に頭に浮かぶのは〜」 =「…と言えば、〜だよね」とも表現できますよ。
ご参考まで!