Fish is correct for most uses. One fish or two fish, it's always fish. BUT, technically if you have different types of fish they are fishes. Two cod are two fish, but one cod and one bass are two fishes. You rarely see this used outside of scientific articles though. Almost everyone just uses fish for singular and plural in all cases.

Fish is both for 1 or 100 fish, even when they are different kinds of fish. But, is used "my brother fishes every day" because brother goes fishing at the lake. It is also used in many slang and colloquial expressions

Fish is correct , it usually use plural.

Hello! We usually use "fish" not "fishes" bcs fish has no plural, so we use "some". First sentence is correct.

Fishes