Kyne & Simpfendorfer.. - Shark Specialist Group

Irvine et al. (2006b) reported female C. crepidater to 54 years and males to 34 years. Irvine et
al. (2006b) trialled the application of both internal and external dorsal spine band counts to
age this species and was able to validate the annual formation of external bands using the
preliminary radiometric age estimates of Fenton (2001). Thus, age estimates from internal
bands (27 years in females, 22 in males) were inaccurate and grossly underestimated age
(Irvine 2004, Irvine et al. 2006b). Preliminary age estimates for P. plunketi are 39 years in
females and 32 years in males (Irvine 2004) (Table 2.8). Somniosus lack dorsal spines and an
examination of vertebrae and neural arches could not identify any bands that may represent
growth (S. Irvine, pers. comm.).
While Irvine et al. (2006b) estimated age at 50% maturity (A 50 ) in female C. crepidater to be
20 years, maturity actually occurred over a wide range of ages (12–42 years), Furthermore,
the youngest gravid female was found to be 27 years old while the youngest carrying nearterm
embryos was 29 years. This has relevance when considering the reproductive
productivity of a species, as it is these older females, several years beyond the estimate of A 50 ,
that are contributing to the population (Irvine et al. 2006b).
Irvine (2004) calculated lifetime fecundities for C. crepidater (utilising a mean litter size of 6
and 34 reproductive years) and P. plunketi (utilising mean litter size of 17 and 10
reproductive years; see Irvine 2004 for details). If these species reproduce biennially, Irvine
(2004) calculated that the lifetime fecundity of a female C. crepidater is 102 pups and of a
female P. plunketi is 85 pups and if these species reproduce triennially the lifetime fecundity
of a female C. crepidater is 68 pups and of a female P. plunketi is 56 pups (Irvine 2004).
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