Francis and Duffy Length at maturity in three pelagic sharks 



493 



mated by split linear regression fitted to 

 sharks longer than 110 cm, at 142.7 cm 

 (95% confidence interval (CI) 140.7-144.7 

 cm) (Fig. 2). Thus rapid elongation of the 

 claspers began at about 110 cm and was 

 completed by 143 cm. Spermatophores 

 first appeared in the posterior reproduc- 

 tive tract at 135 cm and by about 152 cm 

 50% of males contained spermatophores. 

 The percentage of sharks with spermato- 

 phores peaked at 165 cm (82% of males) 

 and then declined to about 50% , although 

 sample sizes were small in the longer 

 length groups (Table 2). 



In females, UWI began increasing 

 at a length of about 145 cm, but many 

 larger, nonpregnant sharks showed no 

 expansion of the uteri (Fig. 3). Three 

 females with UWI of about 4-5% were 

 postpartum, and two with UWI about 

 11% and one with UWI of about 4% were 

 pregnant. Pregnant females measured 

 167-202 cm (mean 184 cm, n = 55). Of 

 19 females longer than 175 cm that were 

 scored by observers for pregnancy, 10 

 (53%) were pregnant, two (11%) were 

 postpartum, and seven (37%) were rest- 

 ing (or possibly immature). 



Apart from a 185-cm pregnant fe- 

 male, all whole porbeagles examined 

 by us were immature; therefore no at- 

 tempt was made to estimate maturity 

 directly. 



Shortfin mako shark 



20 -i 



15- 



10 



 Claspers • embryos (n=6) 



° Claspers - free living (n=322) 



Claspers (split regression) 



Spermatophores present 



%, 



100 



80 t/> 



60 



40 ^ 



80 100 120 

 Fork length (cm) 



140 160 180 200 



Figure 2 



Maturation of male porbeagle sharks iLainna nasus): variation in 

 clasper development and presence of spermatophores in the reproduc- 

 tive tract. 



12- 



10- 



6- 



I I Pregnant females (n=55) 

 o Uterus width index (n=63) 



CLI showed two strong inflection points 

 in male makos; the first at about 140 cm 

 and the second (estimated by split linear 

 regression) at 185.1 cm (CI 182.5-187.7 

 cm) (Fig. 4). The smallest male with 

 spermatophores was 136 cm, but this 

 measurement was an outlier and may 

 have been an error; the next smallest was 

 156 cm. Fifty percent of males contained 

 spermatophores by 178 cm, and 100% by 

 about 235 cm. Sample sizes were reason- 

 able over the transition range but small 

 above 230 cm (Table 2). 



Male makos examined by us showed 

 little overlap in length between immature and ma- 

 ture sharks (Fig. 4), but sample sizes were small in 

 all length classes (Table 2). The smallest mature male 

 was 182 cm and the largest immature male was 183 cm 

 long. The median maturity estimated by probit analysis 

 was 182.9 cm (CI 180.7-185.1 cm) (Fig. 4). 



In females, UWI began increasing at a length of about 

 275 cm, and all larger sharks had expanded uteri (Fig. 5). 

 Only one pregnant female mako has been recorded from 

 New Zealand waters, and it was 290 cm FL (Duffy and 



<& 



Qtfffooo o°q£8 ^"l&pfT 



6C 



- 12 



10 



- 6 



-2 



25 50 75 100 125 150 175 200 225 

 Fork length (cm) 



Figure 3 



Maturation of female porbeagle sharks lLamna nasus): variation in uterus 

 width index, and length-frequency distribution of pregnant females. 



Francis, 2001); no uterus width measurement was avail- 

 able for that shark. The remaining makos over 275 cm 

 were either postpartum or resting. The maximum ovum 

 diameter began increasing in sharks longer than 250 

 cm (in shorter sharks, ova were barely visible or were 

 invisible) (Fig. 6). The diameter of the oviducal gland 

 increased abruptly between 250 and 270 cm, but ovary 

 dimensions showed no abrupt change in size (Fig. 6). 



Median maturity was estimated directly from a sam- 

 ple of 88 females (Table 3). The smallest mature female 



