As the oceans have been overfished,fish has become more and more expensive.

问题描述:

As the oceans have been overfished,fish has become more and more expensive.
请问fish后为什么跟has,
不是应该跟have吗,因为fish这里应该是复数.

fish 做鱼和鱼肉的时候不可数,谓语动词用单数
但是当表示鱼的种类的时候可数,谓语动词用复数