Kyne & Simpfendorfer.. - Shark Specialist Group

16 embryos (Table 2.5). Irvine (2004) found strong correlations between maternal size and
the number of follicles and the number of embryos and within the New Zealand lanternshark
E. baxteri from southern Australia and Yano (1995) found similar results for the black
dogfish C. fabricii from Greenland.
Etmopterids do not appear to have well-defined reproductive seasons, and have a noncontinuous
reproductive cycle with an apparent resting stage after parturition. This is
supported by observations that follicles do not continue to develop throughout gestation (i.e.
gravid females do not possess developing or mature oocytes) and the finding of numerous
large females with inactive reproductive tracts (Yano 1995, Daley et al. 2002, Irvine 2004).
With species exhibiting aseasonal reproductive cycles, the duration of any resting stage after
parturition and prior to next ovulation is difficult to assess as each reproductive stage occur
can be found in any month sampled (Irvine 2004). Furthermore, gestation period has not been
calculated.
Age estimates are available for only two species of lanternshark, and these are unvalidated
and thus should be considered as preliminary (Gennari et al. 2002, Sion et al. 2002, Irvine et
al. 2006a). Irvine et al. (2006a) estimated age from both internal and external bands on the
second dorsal spine of E. baxteri. While there were considerable differences in age
estimations between these techniques (see Table 2.6), Irvine et al. (2006b), in an aging study
of the somniosid Centroselachus crepidater, suggested that internal bands may underestimate
age. Similarly, for E. baxteri, internal bands become unreadable as internal dentine appears to
stop forming in adult fish (Irvine et al. 2006a). As such, count estimates from external bands
are more reliable, and for E. baxteri this technique gives a maximum age of 57 years for
females and 48 years for males, with age at 50% maturity of 30 years for females and 20
years for males (Irvine et al. 2006a). Vertebral band counts for the velvet belly E. spinax from
the Mediterranean present 7 bands for the largest individuals (Gennari et al. 2002, Sion et al.
2002). There is a considerable size difference between E. spinax which rarely reaches
>450mm TL (although can reach 600mm TL) and E. baxteri with reaches 880mm TL
(Compagno et al. 2005).
Irvine (2004) calculated lifetime fecundity for E. baxteri, utilising a mean litter size of 6-12
(variable with maternal size) and the number of reproductive years as 27, and applying either
a two or three year reproductive cycle. If the species reproduces biennially, Irvine (2004)
calculated that the lifetime fecundity of a female E. baxteri is 128 pups, and if it reproduces
triennially, then the lifetime fecundity would be 81 pups.
74