这里的fish为什么不加复数

因为当fish当“鱼肉”讲时，是不可数名词，无复数形式。

n. 鱼；鱼肉；双鱼座；接合板；（非正式）怪人；（非正式）鱼雷

v. 钓鱼，捕鱼；搜寻；打听消息；打捞；用接合板修补
Every year at this season, fishermen go out to sea to fish.

每年到了这个季节，渔民们都会出海捕鱼。

I'll go to the market and fish for what happened to their family.

我去集市上打听一下他们家的消息。

I caught a big fish in the lake today.

我今天在湖里钓了条很大的鱼。

Fish can just live in water.

鱼只能在水里生存。

I had rice and fish for dinner.

我晚饭吃的大米和鱼肉。

This fish dish in particular was delicious.

这道鱼特别好吃。