Should the word "fish" be singular or plural? Single: fish Fish

Should the word "fish" be singular or plural? Single: fish Fish

Fish is a simple compound homograph when it means "fish". When it means plural, it can't add - es, let alone use "much" to modify it
Many fish are raised in the lake
When we need to express different kinds of fish, we can add - es
The paper is about some fresh water fishes