PRATT: REPRODUCTION IN BLUE SHARKS 



Canyon to Georges Bank, They are sexually active 

 with obvious external mating wounds on every 

 individual in shelf waters. The presence of male 

 spermatozoa in the oviducal gland indicates that a 

 large proportion have successfully copulated. 

 Subadults were found inseminated at a minimum 

 size of 135 cm. They bear abrasive scarring on the 

 lateral walls of the vagina in fish as small as 158 

 cm. 



3. Mature females range from 185 to >300 cm 

 long. They possess fully differentiated organ sys- 

 tems that are actively developing eggs, embryos, 

 or both. The ovary is robust with over 100 ova from 

 16 to 21 mm in diameter and hundi'eds of smaller 

 follicles. The oviducal gland is large and heart- 

 shaped with the anterior horns slightly coiled. The 

 uterus when empty is long and flaccid. Skin thick- 

 ness is increased to over twice that of similar-sized 

 males. Recent internal and external mating 

 wounds are usually not present on mature fe- 

 males. Old healed scars are often present on fins 

 and body. 



gravid female that I have examined suggests that 

 another fertilization is imminent. 



ACKNOWLEDGMENTS 



My thanks to the staff of the Oceanic Gamefish 

 Task of the Northeast Fisheries Center Narragan- 

 sett Laboratory, National Marine Fisheries Ser- 

 vice, NOAA, for help in data collection and 

 analysis; to John Casey for guidance and sugges- 

 tions; to Charles Entenmann and the Bay Shore 

 Tuna Club for providing the opportunity to sample 

 at their annual shark tournament; and also to 

 Carol Kroupa and Carl Darenburg, of the Mon- 

 tauk Marine Basin, who made sampling possible 

 during their tournament. Thanks also to Bob 

 Benway and Steve Szlatenyi for photogi'aphy, to 

 Jennie Dunnington for manuscript typing, and to 

 Lianne Armstrong for illustrations and artwork. I 

 am grateful to John Colton who reviewed the 

 manuscript, and to Richard Backus and Francis 

 Williams for permission to use unpublished data. 



Spermatozoa Storage 



Both sexes store spermatozoa. It is first stored in 

 the epididymis of the male in a matrix of suppor- 

 tive tissue, then as spermatophores in the lower 

 ductus deferens. After copulation, spermatozoa is 

 stored as clusters of individuals in tubes of the 

 oviducal gland of the female. Histological sections 

 of oviducal glands from a full size range of 160 

 females revealed spermatozoa stored in 79. 



Sexual Cycle 



Four- and five-year-old female blue sharks ar- 

 rive on the continental shelf off southern New 

 England in late May and early June. Here they 

 sexually interact with males, receiving tooth cuts. 

 The 5 yr olds and some 4 yr olds copulate with 

 males of 180 cm ( 6 yr olds I and larger. The 4-yr-old 

 females are too undeveloped to store spermatozoa. 

 Five-year-old females actively mate and retain 

 copious amounts of spermatozoa. The following 

 spring, this age-group, now 6 yr old, remain off- 

 shore and fertilize their eggs in May or June. Em- 

 bryos reach full term in 9-12 mo. Pupping is from 

 April to July with up to 82 young being born. It is 

 probable that the 7-yr-old female again copulates 

 as the oviducal glands of gravid females contain a 

 relatively small amount of spermatozoa. The full 

 complement of ripe ovarian eggs present in every 



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469 



