Kyne & Simpfendorfer.. - Shark Specialist Group

PART 2. BATOIDS
Order Rajiformes. Batoids.
Family Rhinobatidae. Guitarfishes.
The sole deepwater rhinobatid, the stripenose guitarfish Rhinobatos variegatus is known only
from the holotype collected at 366m depth in the Gulf of Mannar off India. Guitarfishes are
yolk-sac viviparous species producing litters of 1–18 pups annually (Kyne and Bennett 2002),
but there is no specific information available on R. variegatus other than that given in the
original description (Nair and Lal Mohan 1973).
Family Narcinidae. Numbfishes.
Aspects of the general biology of the numbfishes are poorly-known. The family, like other
electric rays is yolk-sac viviparous, but details on the reproductive cycle, fecundity and
maturity, as well as age and growth information is generally lacking. A litter size of 1–2 with
a size at birth of >96mm TL has been observed in the recently described Brazilian blind
torpedo Benthobatis kreffti (Rincon et al. 2001) and a litter size of two in the western
numbfish Narcine lasti with size at birth probably close to 80mm TL (Carvalho and Séret
2002). The Taiwanese blind numbfish B. yangi is known only from a limited number of
specimens detailed in its original description while the dark blindray B. moresbyi is known
only from five specimens (Carvalho et al. 2003). There remains numerous undescribed
species within the family, including the deepwater Narcine sp. C [Last & Stevens, 1994] from
Australia.
Family Narkidae. Sleeper Rays.
There is minimal information on the biology of the sleeper rays. The biology of the rare Natal
sleeper ray Heteronarce garmani is ‘virtually unknown’ (Compagno et al. 1989). The two
endemic New Zealand sleeper rays of the genus Typhlonarke are also rare and poorly-known,
although they reportedly have up to 11 pups per litter with a size at birth of 90–100mm TL
(Duffy 2003a).
Family Torpedinidae. Torpedo Rays.
As with other electric ray families, there is relatively little information on the biology of the
torpedo rays. The biology of some shallower water species (i.e. Torpedo californica, T.
marmorata and T. torpedo) is reasonably well known, but apart from some minimal data on
the New Zealand torpedo ray T. fairchildi and the great torpedo T. nobiliana, there is little
information on the deeper water torpedos. Most are poorly-known and one, the smalldisk
torpedo T. microdiscus, is known only from two specimens collected from submarine ridges
in the Southeast Pacific. A litter size of eight has been reported for T. fairchildi (see Duffy
2003b), while Trunov and Kukuev (2005) noted 35 large follicles in the ovaries of T.
nobiliana from the Azores and Capapé (1974) estimated a gestation period of ~12 months for
that species from Tunisia. Abdel-Aziz (1994) noted that ovarian fecundity in the shallower
water T. torpedo and T. marmorata is higher than uterine fecundity, and as such, actual
fecundity in T. nobiliana is likely lower than the ovarian fecundity of 35 reported by Trunov
and Kukuev (2005). Reported litter sizes for shallower water species are generally small, for
example Abdel-Aziz (1994) reports 2–12 (average 7.2) for T. torpedo and 3–16 (9.3) for T.
marmorata from Egypt, Capapé (1974) 6–10 (8) for T. marmorata from Tunisia, and Neer
and Cailliet (2001) 17 for a single T. californica. Gestation is variable between shallower
water species, Abdel-Aziz (1994) noting an annual reproductive cycle with a gestation period
of 5–6 months in T. torpedo and a probable biennial cycle with a gestation period of 10–12
months for T. marmorata. Ageing studies of the deepwater torpedos are lacking, but T.
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