1. Ovoviviparity: Generally practiced by large sharks. The eggs of sharks are large and their supply of nutrients is not in short supply. The oviposited eggs are encased in a flattened cushion-shaped sheath that is added around the egg as it passes through the oviduct, the outer skin of the sheath hardens when it enters the water, and each corner of the sheath has a short, hollow horn into which seawater can enter to oxygenate the egg. A limited number of eggs are laid at a time. Eggs are in the form of sacks or spirals, and after being laid, they are anchored to coral reefs, benthic plants, or rock crevices. The empty egg sacs that wash up on the shore are nicknamed the "mermaid's purse.

2. Ovoviviparity (non-placental viviparity): Fertilized eggs develop in the uterus and are nourished by the yolk sacs or eggs discharged into the uterus from the ovaries, and the placenta does not form in the uterus. Except for the whale shark, which can produce more than 300 tails at a time, the rest of them can produce at most tens of tails at a time, and the least is the fox shark (thresher shark), which produces only two tails at a time.

3. Fetal (placenta-type fetus): The fertilized egg with a horny shell develops in the uterus, and the nutrients needed for its growth are obtained from the yolk sac placenta, and it is not until the young shark is almost fully formed that it is produced, with dozens of tails being produced at a time. Most pelagic sharks are viviparous. Most sharks breed seasonally each year, with some large sharks breeding every other year. Most sharks are pregnant for 8-9 months, with white-spotted horned sharks being pregnant for up to 24 months. Generally, large sharks produce more young at a time, while small sharks do the opposite. Sharks also grow very slowly and do not reach sexual maturity until they are 5-10 years old