Mutations disprove the theory of upward evolution

[Esquilax]

But they do only produce fish, right.

All fish produce fish. It has never been observed that a fish produce anything but fish.

Cats produce cats.
Dogs produce dogs.

We have no record of anything other than an animal produces the same kind.

Simple science.

So then find me a mainstream scientific source that says that evolution is one species giving birth to offspring of another species, and you might have a point.

Or can't you do that?