THE REPRODUCTIVE BIOLOGY OF THE ATLANTIC SHARPNOSE 

 SHARK, RHIZOPRIONODON TERRAENOVAE (RICHARDSON) 



Glenn R. Parsons 1 



ABSTRACT 



Atlantic sharpnose sharks, Rhizoprionodon terraenovae (Richardson), were collected in the north 

 central Gulf of Mexico from June 1979 to May 1980. The principal sampling devices employed were 

 longline, trawl, and rod and reel. From a total of 215 Atlantic sharpnose sharks obtained during the 

 study, 144 were female and 71 were male, ranging from 30 to 107 cm total lengths. The reproductive 

 anatomy of both male and female sharpnose sharks is described. Atlantic sharpnose sharks differ 

 from other carcharhinids in that the ovary is developed on the left side in females and overlapping 

 siphon sacs are present in males. Clasper development suggests that males mature at about 80 cm 

 total length, while ovarian egg diameters show that female maturation occurs at about 85 cm. 

 Matings occur primarily between mid-May and mid-July. Embryonic growth is rapid immediately 

 after fertilization during summer and fall but declines during winter and spring. Gestation requires 

 10 to 11 months and parturitions probably peak in June. Pups are released near shore at an average 

 total length of 32 cm. Statistical analyses reveal a positive relationship between adult total length 

 and litter size, with the largest individuals being the most fecund. An inverse relationship was 

 observed between the numbers of embryos per uterus and embryo size. Mechanical "packing" 

 within the uterus is proposed to explain the relationship. 



The seasonal distribution of sharpnose sharks was found to be determined by an inshore-offshore 

 migration. The data indicate that during winter months in deeper offshore waters, aggregates of 

 predominately adult female sharpnose sharks may be encountered. The sex ratio at birth was found 

 to be 1:1 but among adults collected a 1:2.8 ratio was observed. 



Studies dealing with the reproductive biology of 

 elasmobranchs have fallen far behind the volu- 

 minous amount of data that have accumulated on 

 reproduction in the teleostean fishes. The north- 

 ern Gulf of Mexico has been an area of particu- 

 lar neglect with only a few rather generalized 

 studies (Springer 1938, 1940, 1950; Baughman 

 and Springer 1950). Springer's (1960) classic 

 work on the natural history of the sandbar shark, 

 Careharhinus milberti (Eulamia milberti), con- 

 tains a great deal of reproductive information 

 that might be applied to carcharhinid sharks in 

 general. Likewise, Clark and von Schmidt's 

 (1965) survey of the sharks of the central gulf 

 coast of Florida provided valuable reproductive 

 data. The understanding of the life history of the 

 blue shark, Prionace glauca, was furthered by 

 Pratt's (1979) examination of its reproductive 

 biology. 



Data concerning the life history of Rhizoprion- 

 odon terraenovae are scarce. Rhizoprionodon spe- 

 cies are believed to be born in the late spring and 



•Department of Biological Sciences, University of South 

 Alabama, Mobile, AL 36688; present address: Department of 

 Marine Science, University of South Florida, 140 Seventh Ave- 

 nue South, St. Petersburg, FL 33701. 



Manuscript accepted June 1982. 



FISHERY BULLETIN: VOL. 81, NO. 1. 1983. 



summer. Bigelow and Schroeder (1948) reported 

 that recently born specimens can be collected 

 from Florida in July and that they were also 

 present off the mouth of the Mississippi River in 

 August. Skocik (1969) reported that pups are 

 usually born in the spring but no data were avail- 

 able on mating season or gestation period. 



Rhizoprionodon species are viviparous, the 

 embryos obtaining nourishment via a placental 

 connection (sometimes called a "pseudo- or yolk- 

 sac placenta") between mother and embryo. Fe- 

 cundity in Rhizoprionodon has been variously 

 reported. Baughman and Springer (1950) report- 

 ed four embryos for R. terraenovae. Bass et al. 

 (1975) found an average of 4.7 embryos with a 

 range of two to eight in R. acutus. Skocik (1969) 

 reported a litter size of 12 for R. terraenovae, 

 while Bigelow and Schroeder (1948) reported the 

 same number for R. terraenovae taken around 

 Cuba. Clark and von Schmidt (1965) briefly sur- 

 veyed R. terraenovae off Englewood, Fla., and 

 found one 83 cm female with five eggs. They also 

 reported that all adult females examined had 

 functional left ovaries. Compagno (1978) report- 

 ed a range of one to four embryos for R. porosus. 

 The pups of R. terraenovae have been reported to 

 be 11 to 16 in (27.9 to 40.6 cm) at birth (Baugh- 



61 



