(Before I start, I just want to remind everyone that I am relying heavily on RTB’s model and sources rather than my own knowledge. So don’t get your butt hurt if I forget to properly cite the information I get from them. Just about everything I say is coming from them. So keep that in mind)
Depending on which translation you read, Genesis 1:21 suggests that whales, all sea mammals, and all birds, which would probably be considered “species” along with humans:
And God created the great sea monsters, and every living creature (nephesh) that moves, with which the waters swarmed after their kind, and every winged bird after its kind; and God saw that it was good.
According to Genesis, God also created three specialized kinds of land mammals: “a) short-legged land mammals, b) long-legged land mammals that are easy to tame, and c) long-legged land mammals that are difficult to tame—all three specifically designed to cohabit with humans.”
However, Genesis doesn’t clarify the issue of how we should define “kinds” since it seems to represent a diverse group of animals and plants. For instance, most Hebrew scholars think “kinds” probably refers to what biologists would classify as genera or families, but there are certain verses in the bible that suggest a broader definition:
These, moreover, you shall detest among the birds; they are abhorrent, not to be eaten: the eagle and the vulture and the buzzard, and the kite and the falcon in its kind, ( Leviticus 11:13-14 )
every raven in its kind, ( Leviticus 11:15 )
and the ostrich and the owl and the sea gull and the hawk in its kind, ( Leviticus 11:16 )
and the little owl and the cormorant and the great owl, and the white owl and the pelican and the carrion vulture, and the stork, the heron in its kinds, and the hoopoe, and the bat. ( Leviticus 11:17-19 )
These of them you may eat: the locust in its kinds, and the devastating locust in its kinds, and the cricket in its kinds, and the grasshopper in its kinds. ( Leviticus 11:22 )
Now these are to you the unclean among the swarming things which swarm on the earth: the mole, and the mouse, and the great lizard in its kinds, and the gecko, and the crocodile, and the lizard, and the sand reptile, and the chameleon. ( Leviticus 11:29-30 )
But these are the ones which you shall not eat: the eagle and the vulture and the buzzard, and the red kite, the falcon, and the kite in their kinds, ( Deuteronomy 14:12-13 )
and every raven in its kind, ( Deuteronomy 14:14 )
and the ostrich, the owl, the sea gull, and the hawk in their kinds, ( Deuteronomy 14:15 )
the little owl, the great owl, the white owl, the pelican, the carrion vulture, the cormorant, the stork, and the heron in their kinds, and the hoopoe and the bat. ( Deuteronomy 14:16-18 )
…Their fish will be according to their kinds, like the fish of the Great Sea, very many. ( Ezekiel 47:10 )
These verses suggest that the “kinds” could be classified as genera, family, and Orders. Therefore, the “kinds” seen in Genesis one probably does not represent species.
Genesis 1:21 is referring to sea mammals because “creature” in Genesis means “Nephesh”. Read this source for more:
Which Animals Are Nephesh Animals? - Reasons to Believe