FISHERY BULLETIN: VOL. 81. NO. 1 



total length at maturity. The smallest mature 

 individuals were about 80 cm and possessed si- 

 phon sacs about 23% of total length. 



Females 



Maturation in females was determined by ex- 

 amining the developing ovary and ovarian eggs. 

 Females were found to mature at a greater total 

 length than males. The ovary does not begin to 

 develop until the individual reaches about 60 cm 

 TL. Figure 10 shows that development reaches 

 an asymptote between 85 and 90 cm TL. Even 

 among individuals of the same size taken during 

 the same month there is a high degree of varia- 

 tion in ovarian length. For this reason ovarian 

 length is not considered a good indicator of ma- 

 turity in Atlantic sharpnose shark. 



Changes in the diameter of ovarian eggs were 

 found to be a reliable indicator of the beginning 

 of maturation. Figure 11 shows the first genera- 

 tion of ovarian eggs produced by the subadult 

 population. Increase in egg diameter begins at 

 60 to 65 cm TL, at about the same time the length 

 of the ovary begins to increase. The eggs increase 

 in diameter until the first ovulation, which oc- 

 curs at about 85 to 90 cm TL. Most female sharp- 

 nose sharks mature within this size range. 



Several female sharpnose sharks that had re- 

 cently matured were examined. One individual 

 of 88 cm TL, collected in late May, had full-sized 

 ovarian eggs and had apparently recently mated 

 due to the numerous mating scars that were ob- 

 served in the region between the first and second 



I0-4T 



>- 

 cr 



88  



I 7-3 + 



5 57 + 



2 6 



o 

 o o 



o 



I . • o 



o o 

 o o o 



oo 



•••••• . 



ooo o • I 



o o o g 



oo o o 

 o 

 o 



o OBSERVED 



• REGRESSION ESTIMATED 



50 60 70 80 90 



TOTAL LENGTH fcrW 



100 110 



Figure 10.— Regression analysis showing development of the 

 ovary in Atlantic sharpnose sharks, N = 42. Maturation is esti- 

 mated to be complete at 85 to 90 cm total length. 



CT 

 (li 

 H 

 ld 



< 



Q 



(a 

 to 



< 



cr 



o 



25 T 



20 



15- 



10 • 



1st OVULATION 



•-• •- 



• • 



-+- 



■+- 



-+- 



40 50 60 70 80 



TOTAL LENGTH (cm) 



90 



100 



Figure 11. — Maturation of female Atlantic sharpnose sharks 

 as evidenced by the increase in ovarian egg diameter. Hand-fit 

 curve approximates the increase in ovarian egg diameter from 

 juvenile to first ovulation, N = 63. 



dorsal fins. An 86 cm individual, collected in 

 early July, possessed six ova (8 to 10 cm), while 

 another 89 cm female, collected in mid-July, pos- 

 sessed uterine eggs. In late August, all mature 

 females examined contained embryos. The small- 

 est gravid specimens were 87, 88, and 89 cm TL 

 and contained 11, 8, and 6 cm embryos, respec- 

 tively. These observations further support the 85 

 to 90 cm estimated size at maturity. 



Mating Season 



Twenty-three reproductively active male At- 

 lantic sharpnose sharks were examined to delin- 

 eate the mating season. A gonadosomatic index 

 (GSI), testis weight expressed as percent total 

 body weight, was found to be the best indicator of 

 mating season. 



The GSI provided a defined mating season for 

 male sharpnose sharks (Fig. 12). Reporting on 

 central gulf coast of Florida populations, Clark 

 and von Schmidt (1965) suggested that small 

 shark species (such as Mustelus norrisi and Scoli- 

 odon terraenovae = Rhizoprionodon terraenovae) 

 mate and bear young in the late winter and early 

 spring. In the north central gulf, contrary to 

 Clark and von Schmidt's findings for Florida, 

 male sharpnose sharks appear to be reproduc- 

 tively active during late spring and summer. 

 From about September to March, the GSI was 

 found to be low, 0.2 to 0.37. During these months 

 specimens were observed to have reduced testes 



68 



