Evidence suggests that certain dogfish species can live 70 years. Many of the large shark species reproduce every other year. Many females are thin and emaciated when they reach full term. Alternate year pupping may be required for the female to store sufficient nutrients to pass to the offspring. Some species such as the blue, hammerhead, sand tiger, and sharpnose sharks reproduce every year, as do most of the egglaying species.
Male sharks are as reproductively complex as the females.
Internal fertilization is accomplished using one or both claspers, which are rod-like appendages of the male's pelvic fins. Claspers are rotated and inserted into the female's vagina after a sometimes elaborate but poorly known courtship process in which the male bites the female's fins and flanks until she is receptive. The maneuvering to permit copulation must be complex, especially with females weighing thousands of pounds. The clasper is anchored in the female by terminal spurs or sharpened expendable ridges and spermatozoa are transferred in a stream of water driven by paired siphon sacs. These sacs are a muscle-driven hydraulic system in the abdominal wall of the males.