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Biological vulnerability of two exploited sharks of the genus Deania (Centrophoridae)

journal contribution
posted on 2023-05-19, 05:19 authored by Irvine, SB, Daley, RK, Graham, KJ, Stevens, JD
Life-history parameters of Deania calcea and Deania quadrispinosa suggested that their productivity was very low. Maturity (LT50) occurs at c. 80% of maximum observed total lengths (LT) for both species and sexes. A large proportion of mature females were neither pre-ovulatory nor pregnant, and the reproductive cycle included a distinct resting phase after pregnancy. For D. calcea, mean ovarian fecundity was 12 and maximum observed litter size was 10 (average of six); D. quadrispinosa averaged 17 pups per litter. Birth LT was 28–33 cm for D. calcea and 23–25 cm for D. quadrispinosa. The male and female reproductive cycles were aseasonal, and consequently, the length of the reproductive cycle could not be determined. Preliminary ageing data from dorsal-spine growth bands suggested that female D. calcea lived to 31–36 years and males to 24–32 years. The LT-at-age data using external bands on the spines showed maturity occurring at 15·5 years (males) and 21·5 years (females), whereas banding on the internal dentine indicated maturity at 10·5 and 17·5 years for males and females. Thus, a female lifetime of 31–36 years allowed for a maximum of 7 litters if a 2 year cycle is assumed or only five litters with a 3 year cycle, resulting in a lifetime fecundity of only 42 pups (2 year cycle) or even lower (3 year cycle).

History

Publication title

Journal of Fish Biology

Volume

80

Issue

5

Pagination

1181-1206

ISSN

0022-1112

Department/School

Institute for Marine and Antarctic Studies

Publisher

Blackwell Publishing Ltd

Place of publication

9600 Garsington Rd, Oxford, England, Oxon, Ox4 2Dg

Rights statement

Copyright 2012 The Authors Journal of Fish Biology © 2012 The Fisheries Society of the British Isles

Repository Status

  • Restricted

Socio-economic Objectives

Environmental lifecycle assessment

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