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Advances in the aquatic sciences
RESEARCH ARTICLE

Towards better management of Australia’s shark fishery: genetic analyses reveal unexpected ratios of cryptic blacktip species Carcharhinus tilstoni and C. limbatus

J. R. Ovenden A C , J. A. T. Morgan A , T. Kashiwagi A , D. Broderick A and J. Salini B
+ Author Affiliations
- Author Affiliations

A Molecular Fisheries Laboratory, Queensland Primary Industries and Fisheries, PO Box 6097, St Lucia, QLD 4069, Australia.

B CSIRO Marine Laboratories, Cleveland, QLD 4163, Australia.

C Corresponding author. Email: jennifer.ovenden@dpi.qld.gov.au

Marine and Freshwater Research 61(2) 253-262 https://doi.org/10.1071/MF09151
Submitted: 19 June 2009  Accepted: 24 August 2009   Published: 25 February 2010

Abstract

The common blacktip shark (Carcharhinus limbatus) and the Australian blacktip shark (C. tilstoni) are morphologically similar species that co-occur in subtropical and tropical Australia. In striking contrast to what has been previously reported, we demonstrate that the common blacktip shark is not rare in northern Australia but occurs in approximately equal frequencies with the Australian blacktip shark. Management of shark resources in northern Australia needs to take account of this new information. Species identification was performed using nucleotide sequences of the control, NADH dehydrogenase subunit 4 (ND4) and cytochrome oxidase I (COI) regions in the mitochondrial genome. The proportion of overall genetic variation (FST) between the two species was small (0.042, P < 0.01) based on allele frequencies at five microsatellite loci. We confirm that a third blacktip species (C. amblyrhynchoides, graceful shark) is closely related to C. tilstoni and C. limbatus and can be distinguished from them on the basis of mtDNA sequences from two gene regions. The Australian blacktip shark (C. tilstoni) was not encountered among 20 samples from central Indonesia that were later confirmed to be common blacktip and graceful sharks. Fisheries regulators urgently need new information on life history, population structure and morphological characters for species identification of blacktip shark species in Australia.

Additional keywords: blacktip shark, COI, control region, cytochrome oxidase I, fisheries, Indonesia, NADH dehydrogenase subunit 4, ND4, species identification.


Acknowledgements

We sincerely thank tissue sample collectors including Rik Buckworth, Dharmadi, Fahmi, Jenny Giles, Rory McAuley, Stirling Peverell, Richard Pillans, Colin Simpendorfer, Jason Stapely, Chris Tarca, Steve Taylor, David Welch and William White. Malcolm Dunning, Warwick Nash, Wayne Sumpton and two anonymous reviewers kindly provided comments on earlier versions of the text. The Australian Fisheries Research and Development Corporation made financial contributions to this study.


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