And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good. And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth. And the evening and the morning were the fifth day.
During the fifth day, God created the fish and fowls. Both were given the responsibility to be fruitful and multiply. But there were two stipulations – 1) they were to fill their specific place, the fish were to fill the waters, while the fowl were to fill the earth, 2) they were to reproduce after their own kind, fish were to produce fish, while fowls were to produce fowls. God’s plan from the very beginning was for His creation to be fruitful and multiply and reproduce after its own kind.