Complex sentence: A year later, the whale grew too big to keep in captivity, though smaller than average, and was released on April 1,1998; he was the second and probably the last baleen whale to be kept in captivity.
Split into simpler sentences: A year later, the whale grew too big to keep in captivity, though smaller than average, and was released on April 1,1998. He was the second and probably the last baleen whale to be kept in captivity.