I went back and re-read the Bible account of Noah and the Flood. It says that God destroyed all the things living on the earth, as in mammals and birds and things that creep, or scurry, on the ground. Nowhere did it say that God destroyed the fish. God also told them to take seven pairs of all the animals which were permitted to be eaten - fish were allowed, but not taken - I would conclude this to mean because they weren't destroyed. Just my interpretation.
Seven of each of the "clean" animals and two of each of the "unclean" reference the Law of Moses. This is a dead giveaway that this particular version of Noah's story came AFTER the Jews had the law and was written about this event in the same way we talk about the Kennedy Assaination.
Further, you already have a problem with enough space on this ark for even two of each animal. So, adding more doesn't make the story more believable.
Moreover, what did the carnivores eat after the flood until the animal population could replenish itself?
The balance of nature is not something you can aritifically tamper with and get good results.
Supporting the Noah's Flood story with apologia damages our credibility and, frankly, makes us all sound rather incredibly naive and uninformed.
Better to view it as another version of the Babylonian Gilgamesh Epic.
Enki rules!!