Wow! Have you found anyone other than yourself that fits this category? Young-earth, six-day creationists are virtually certain to also believe in a global flood and Noah's ark. This makes it impossible to also believe in fixed species since there are far too many (several to a few tens of millions) to fit on the ark.
So I assume you reject the story of Noah's Ark?
There are few, but do scientists are normally not that great at finding what animals fit into "species." It would take forever to see which of the supposed millions of species of animals can reproduce.
Can't be very many considering even AiG rejects the vapor canopy as unworkable.
It's an unproven story, probably based on oral history swollen in the telling from one generation to the next.
"since there are far too many (several to a few tens of millions) to fit on the ark"...
Unless the ark were bigger on the inside than on the outside...
There were some mighty strange things about the Ark. First off, no one knows what "gopher wood" was...