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RESEARCH ARTICLE

Reproduction of Heterodontus portusjacksoni in Victoria, Australia: evidence of two populations and reproductive parameters for the eastern population

Javier Tovar-Ávila A B C D E , Terence I. Walker A B and Robert W. Day A
+ Author Affiliations
- Author Affiliations

A Department of Zoology, The University of Melbourne, Parkville, Vic. 3010, Australia.

B Primary Industries Research Victoria, PO Box 114, Queenscliff, Vic. 3225, Australia.

C Instituto Nacional de la Pesca, Pitágoras 1320, Sta. Cruz Atoyac 03310, D.F., México.

D Present address: CRIP Bahía de Banderas, A.P. 59 Bucerías, Nayarit 63732, México.

E Corresponding author. Email: javiert@icmyl.unam.mx

Marine and Freshwater Research 58(10) 956-965 https://doi.org/10.1071/MF06230
Submitted: 29 November 2006  Accepted: 20 September 2007   Published: 30 October 2007

Abstract

Significant differences in the length–frequency composition of catch samples, mass–length relationships and length-at-maturity found between Heterodontus portusjacksoni from western and far-eastern Victoria, suggest the presence of at least two separate breeding populations off south-eastern Australia, with some mixing between these regions. In each region females attain a larger size than males, and collectively those sharks in western Victoria are smaller, present higher mass-at-length, and lower length-at-maturity than those in far-eastern Victoria. These regional differences might be a result of sampling bias, length-selective fishing mortality, environmental conditions, or genetic differences. However, tagging evidence from previous studies and the presence of two bio-geographic provinces in the region support the hypothesis of two separate breeding populations. The essential reproductive parameters for H. portusjacksoni population analysis in far-eastern Victoria were determined, using a novel method to estimate fecundity and the ovarian cycle of an egg-laying species. In this region, females have between 6 and 20 pre-ovulatory oocytes (average = 14, n = 29, standard deviation = 3.71) before the reproductive season. The species has an annual reproductive cycle correlated with water temperature, with ovulation starting during late winter to early spring and a ~6 month egg-laying period. The period from the onset of vitellogenesis to ovulation of oocytes is ~18 months.

Additional keywords: chondrichthyans, Port Jackson shark.


Acknowledgements

We thank the anonymous referees who improved this paper with their comments and corrections. Matt Reardon is acknowledged for helping with the dissection of some specimens, and Ken Smith, Susan Smith and commercial fishers from Victoria for helping with sample collection. This research was supported by an Australian Fisheries Research and Development Corporation grant (FRDC Project 2003/023 to Terence I. Walker). The principal author was supported by a Postgraduate Scholarship from the National Science and Technology Council (CONACyT) and the National Fisheries Institute (INP) from Mexico and by a David Hay Writing Up Award from the University of Melbourne for preparation of this paper.


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