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Fishery Bulletin 103(3) 



the length at which rapid expansion of the uterus be- 

 gan (145 cm) and the length of the smallest pregnant 

 female (167 cm). UWI values less than 2% occurred for 

 females up to about 185 cm (Fig. 3), but this does not 

 mean that a high proportion of females in this length 

 group had narrow uteri; uterus width measurements 

 were not available for most of our pregnant females and 

 therefore large UWI values are underrepresented in 

 Figure 3. Most pregnant females were 170-200 cm long. 

 We estimate that median maturity in females is about 

 170-180 cm, but this estimate requires confirmation. 

 It is essentially the same as that provided by Francis 

 and Stevens (2000) for New Zealand and Australian 

 porbeagles (their New Zealand data were a smaller 

 subset of the data used in the present study). 



Although our estimates of median maturity for both 

 males and females are uncertain, it is clear that por- 

 beagles from New Zealand mature at considerably 

 smaller lengths than they do in the North Atlantic. 

 In the western North Atlantic, males mature at about 

 166 cm and females at 208 cm (Jensen et al., 2002). 

 Data from the eastern North Atlantic (Gauld, 1989; 

 Ellis and Shackley, 1995) are insufficient to estimate 

 length at maturity, but the pregnant females reported 

 by Gauld (1989) were considerably longer (199-248 cm) 

 than those from New Zealand. 



Porbeagles from the North Atlantic also grow larger 

 than those from New Zealand: in the North Atlantic, 

 sharks longer than 200 cm are common (Gauld, 1989; 

 Campana et al., 2001), whereas around New Zealand 

 and Australia they are very rare (Francis et al., 2001; 

 Stevens and Wayte 4 ). Differences in length at maturity 

 between the North Atlantic and New Zealand and the 

 proportion of sharks in the longer length classes indi- 

 cate the existence of separate populations in the two 

 regions — a conclusion that is supported by the disjunct 

 distribution of porbeagles in the Northern and Southern 

 Hemispheres (Compagno, 2001). 



Shortfin mako shark 



Our direct maturity estimate for male makos (183 cm) 

 was based on a small sample size, and the small overlap 

 between the lengths of immature and mature sharks 

 is implausible. However, the lengths at which clasper 

 development was completed, and at which 50% of males 

 had spermatophores, were similar to the direct estimate 

 (Table 4). Median maturity for males is therefore about 

 180-185 cm. 



Our direct maturity estimate for female makos 

 (280 cm) was based on few sharks over the matura- 

 tion length range but was consistent with the length 

 at which rapid uterus expansion began (275 cm). Our 

 best estimate of median maturity in females is 275- 

 285 cm. 



Stevens (1983) used the degree of clasper calcifica- 

 tion and an inflection in clasper length to estimate the 

 length at maturity of males from New South Wales 

 as 176 cm. In South Africa, males were estimated to 

 mature at 177-188 cm (Cliff et al., 1990), but very few 

 immature sharks were available. Our estimate of me- 

 dian maturity in New Zealand males (180-185 cm) is 

 therefore similar to those from elsewhere. 



Mollet et al. (2000) reported lengths at maturity for 

 female makos of 298 cm total length in the Northern 

 Hemisphere and 273 cm total length in the Southern 

 Hemisphere. However, some of the 25 cm difference was 

 due to Northern Hemisphere measurements having been 

 taken over the curve of the body and Southern Hemi- 

 sphere measurements having been taken in a straight 

 line. Using appropriate conversion regressions, their 

 Northern Hemisphere median maturity is equivalent 

 to 267 cm FL, and their Southern Hemisphere median 

 maturity is equivalent to 248 cm FL. When Mollet et 

 al.'s Southern Hemisphere data are analysed separately 

 for two subregions, South Africa and Australia, the 

 estimated lengths at maturity are 244 cm (n = 50) and 

 254 cm (n = 32) respectively (Mollet 5 ). The former is con- 

 sistent with Cliff et al.'s (1990) estimate of 243 cm for 

 South Africa, and the latter is consistent with Stevens's 

 (1983) estimate of 255 cm for eastern Australia (both 

 those estimates were made from subsets of the data 

 used by Mollet et al. [2000]). 



Our estimate of median maturity in New Zealand 

 females (275-285 cm) is substantially higher than Mol- 

 let's 5 estimate for Australia (254 cm). Because tagged 

 makos have moved between New Zealand and eastern 

 Australia in both directions (Chan, 2001; Hartill and 

 Davies, 2001; Holdsworth and Saul, 2003), we think it 

 is unlikely that the difference is due to the presence 

 of distinct populations in the two regions. We suspect 

 that the difference is a result of possible length estima- 

 tion errors (some of the Australian shark lengths were 

 calculated from recorded weights, with a length-weight 

 regression [Stevens, 1983; Mollet et al., 2000]), and 

 the result of small sample sizes over the length range 

 at maturation. For our direct maturity estimate, we 

 had only 19 New Zealand sharks over the length range 

 240-290 cm, and Mollet 5 had 15 sharks. 



Interestingly, our estimate of median maturity in New 

 Zealand females is also greater than Mollet et al.'s (2000) 

 estimate for the western North Atlantic, thus removing 

 the reported between-hemisphere difference. We believe 

 that larger, accurately measured samples of female ma- 

 kos are required before definitive statements can be 

 made about length at maturity in the various regions. 



Blue shark 



In male blue sharks from New Zealand, CLI lacked an 

 inflection near the length of maturity — a feature that 



4 Stevens, J. D., and S. E. Wayte. 1999. A review of Aus- 

 tralia's pelagic shark resources. FRDC Proj. Rep. 98/107, 

 64 p. [Available from CSIRO Marine Research, PO Box 

 1538, Hobart, Tasmania 7001, Australia.] 



5 Mollet, H. 2004. Personal commun. Moss Landing Marine 

 Laboratories, 8272 Moss Landing Road, Moss Landing, CA 

 95039. 



