Few people have witnessed the mating activity of sharks.
In smaller, more flexible species the male coils around the female.
In larger, more rigid species the male orients himself parallel and head-to-head with the female.
During mating, males of many species bite females on the pectoral fins or the middle of the back to hold onto them. Females often bear scars or marks. Upon examination, these marks show they have been made by upper jaw teeth. In some elasmobranchs, males have longer, narrower teeth than females. In some female sharks, such as the blue shark, the skin on the back and flanks is more than twice as thick as the skin on the male.
Shark and batoid eggs are fertilized internally, as opposed to external fertilization in many bony fishes. Internal fertilization is a key adaptation for energy-intensive reproduction.
When born or hatched, young sharks are fully formed and physically able to fend for themselves.
Because these independent shark pups have a better chance for survival, the number of sharks produced in a litter is rarely more than 100. The majority of the species bear far fewer pups.