 Eggs in the North Sea and the Atlantic take 10 – 12 months to hatch , while those from the southern Mediterranean take 7 months to hatch . The length at hatching is 16 cm ( 6 @.@ 3 in ) off Britain , and 10 – 12 cm ( 3 @.@ 9 – 4 @.@ 7 in ) off France . Newly hatched sharks grow at a rate of 0 @.@ 45 – 0 @.@ 56 mm ( 0 @.@ 018 – 0 @.@ 022 in ) per day , and have prominent saddle markings . Sexual maturity is attained at a length of 77 – 79 cm ( 30 – 31 in ) , which corresponds to an age of four years if hatchling growth rates remain constant . This species has a lifespan of at least 19 years . 
