Courtship behavior has never been observed in the wild or in captivity. As for the size and number of the white shark pups, one often-questioned report from the Mediterranean described a female with nine embryos two feet long and 108 pounds each. The reason for the questionability of the account is that free-swimming specimens have been caught at five feet in length and only fifty to sixty pounds in weight. Larger white sharks, quite possibly accurately measured but not scientifically confirmed, have been reported. Fishermen and sailors have reported sighting individual sharks estimated at twenty-five feet in length.
Limited studies suggest that the growth rate of white sharks varies with geography.
Those in the Atlantic appear to grow at a rate of approximately 20 cm per year, compared with 25 to 30 cm per year for younger, and 22 cm per year for older individuals in the eastern Pacific. A 16-foot white shark from the Atlantic is estimated to be twenty years old. But an individual of the same size in the eastern Pacific is estimated to be only thirteen or fourteen years old. The oldest of the ancient sharks are known only from fossilized teeth embedded in rock of the Late Middle Devonian. One shark, known as Cladoselache , is known from teeth, vertebrae, and rare impressions of skin, kidneys and muscles discovered in shales along the shore of Lake Erie.