Journal of Fish Biology (2010) 77, 1165–1172 doi:10.1111/j.1095-8649.2010.02770.x, available online at wileyonlinelibrary.com Genetic data show that Carcharhinus tilstoni is not confined to the tropics, highlighting the importance of a multifaceted approach to species identification J. J. Boomer*†, V. Peddemors‡ and A. J. Stow* *Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia and ‡Cronulla Fisheries Research Centre of Excellence, P.O. Box 21, Cronulla, NSW 2230, Australia (Received 26 June 2010, Accepted 9 August 2010) This study shows a range extension for the Australian blacktip shark Carcharhinus tilstoni, which was believed to be restricted to Australia’s tropical waters, of >1000 km into temperate waters, revealing its vulnerability to a wider commercial fishery. © 2010 The Authors Journal compilation © 2010 The Fisheries Society of the British Isles Key words: blacktip shark; Carcharhinus limbatus ; mtDNA; shark fishery; species distribution. Sharks are proving to be especially vulnerable to anthropogenic pressures, in part this is a response to the K-selected natural-history traits that characterize many species along with pressure from targeted and non-targeted fishing activities (Stevens et al., 2000). In many cases, species distributions span state and international management boundaries, across which protection and management processes may vary for any given species (Last & Stevens, 2009). Therefore, effective conservation and manage- ment require knowledge of species distributions. Despite the size and notoriety of sharks, distributions of some species remain uncertain due to limited opportunities for observation or difficulties with species identification. Sharks, especially those in the carcharhinid family, can be very difficult to identify to species level using morphological features (Chan et al., 2003). Distinguishing features for some species are few, and sharks caught by commercial fishers often have important features removed (e.g. head and teeth) before being landed ashore, making reliable identification very difficult (Chan et al., 2003; Last & Stevens, 2009). The fin trade exacerbates problems with identifying harvested sharks. A solution has been found with the development of DNA markers for species identification. Over the last decade, rapid improvements in DNA technology have seen a suite of markers developed which require only a small sample of tissue for reliable species identification (Chapman et al., 2003; Greig et al., 2005; Ward et al., 2008). The use of this technology has resulted in further taxonomic revision and improved †Author to whom correspondence should be addressed. Tel.: +61 2 9850 8143; fax: +61 2 9850 7972; email: jessica.boomer@mq.edu.au 1165 © 2010 The Authors Journal compilation © 2010 The Fisheries Society of the British Isles