How do manta rays reproduce?

Manta rays bear live young. The single fertilized egg develops inside the mother. The gestation period is unknown. It appears that mantas do not breed until their winglike pectoral fins reach a length of 13-15 feet. There is no specific breeding season: males and females mate year round. The newborns are fairly large, weighing 20-30 pounds, have fins that span 4 feet, and can generally protect themselves from predators