Kyne & Simpfendorfer.. - Shark Specialist Group

Ebert and Davis 2007). These are the only skates for which this has been observed. The big
skate can carry 2–7 embryos per egg case, with an average of 3–4 (Hitz 1964).
There have been several ageing studies of rajid species, and while some are unvalidated and
others preliminary, late maturity has again been demonstrated for the skates. Du Buit (1977)
estimated a maximum age of 50 years for Dipturus batis while longevity of at least 20 years
has been confirmed for A. radiata from skates tagged off Newfoundland (Templeman 1984).
Ageing and growth estimates follow the general trend that larger species are slower growing
and longer-lived than the smaller, faster-growing species (Sulikowski et al. 2005b).
Ebert (2005) estimated the number of reproductive years for several skate species by
considering age at first maturity and maximum observed age. Estimates for deepwater rajid
skates ranged from 13 reproductive years for D. batis and D. innominatus (from Du Buit 1977
and Francis et al. 2001, respectively), through 9 years for Leucoraja wallacei (from
Walmsley-Hart et al. 1999), 6 years for L. naevus and D. pullopunctata (from Du Buit 1977
and Walmsley-Hart et al. 1999, respectively), to 4 years for Raja rhina and D. nasutus (from
Zeiner and Wolf 1993 and Francis et al. 2001, respectively) and 1–3 years for R. binoculata
(from Zeiner and Wolf 1993) (Ebert 2005). Considering some more recent publications (see
Table 2.15) similar estimations would give 3–6 reproductive years for female Amblyraja
georgiana (from Francis and Ó Maolagáin 2005), 7 years for D. chilensis (from Licandeo et
al. 2006) and 4 years for L. naevus (from Gallagher et al. 2004). The age estimations of
McFarlane and King (2006) give considerably more reproductive years for both R. binoculata
(17 years) and R. rhina (19 years) than those calculated from Zeiner and Wolf (1993).
Estimates of annual and lifetime fecundity of rajid skates are highly variable between species.
Annual fecundity has been estimated as 140 egg cases for R. clavata (shelf species; Holden
1975), 90 for R. brachyura (shelf species; Holden et al. 1971) and L. naevus (Du Buit 1976),
60 for R. montagui (shelf species; Holden et al. 1971), and 10–20 for A. radiata (Berestovskii
1994). Ebert and Davis (2007) calculated that annual fecundity in R. binoculata may reach
1260 based on assuming an average of 3.5 embryos per egg case, and egg-laying rates of 360
egg cases per year in captivity (K. Lewand, pers. comm. in Ebert and Davis 2007). Ebert
(2005) extrapolated the annual fecundity of R. clavata to calculate a lifetime fecundity of
~980 egg cases based on the ageing estimates of Ryland and Ajayi (1984). For R. montagui,
Ebert (2005) estimated annual production to be