New Zealand Journal of Marine and Freshwater Research abstracts
Age, growth, and sexual maturity of two New Zealand endemic skates, Dipturus
nasutus and D. innominatus
MALCOLM P. FRANCIS
CAOIMHGHIN Ó MAOLAGáIN
DARREN STEVENS
National Institute of Water & Atmospheric
Research Ltd
P. O. Box 14 901
Wellington, New Zealand
email: m.francis@niwa.cri.nz
Abstract Rough and smooth skates (
Dipturus nasutus
(Banks 1841) and
D. innominatus (Garrick & Paul 1974)) were aged by
counting growth bands on X-rays of thick sections of vertebral centra. Band
counts were imprecise, but there was no between-reader bias. Age estimates were
not validated. The oldest rough skate was 9 years old, but few were more than 6
years old. Females may live longer than males. The combined sexes von
Bertalanffy growth curve was
Lt = 91.3 (1 - e
-0.16[t
+ 1.20]). Half the males matured by c. 52 cm pelvic length (PL) and
4 years, and females by 59 cm PL and 6 years. The oldest smooth skate in
the sample was 24 years, but longevity probably exceeds that. Females appear to
live longer than males. The combined sexes von Bertalanffy growth curve was:
Lt = 150.5 (1 - e-0.095[t + 1.06]). Half the
males matured by c. 93 cm PL and 8 years, and females by 112 cm PL
and 13 years. Smooth skate are late maturing and long-lived relative to other
skates, whereas rough skate are early maturing with a moderate life span.
Keywords age; growth; maturity; longevity; weight; skates;
Dipturus nasutus; Dipturus innominatus
M00088
Received 8 December 2000; accepted 7 February 2001
PDF file of entire paper: medium quality (1233K); (scanned from paper original: notes about this process)
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