Gestation lasts 10 to 12 months and the average calf is 23 feet long and weighs 4,440 pounds at birth. A calf is fed by its mother for seven to eight months. Blue whales once were considered too difficult to hunt because of their speed and tremendous size. However, with the introduction of factory ships and the harpoon gun in the 1920s, blue whales were hunted intensively. By the 1960s they were nearly extinct.
Blue whales face threats from entanglement in fishing nets, pollution, and illegal whaling.
Appendix I listed species cannot be traded commercially. Appendix II listed species can be traded commercially only if trade does not harm their survival.