Rediscovery and redescription of the smoothtooth blacktip shark, Carcharhinus leiodon (Carcharhinidae), from Kuwait, with notes on its possible conservation status

Abstract

Abstract. The smoothtooth blacktip shark, Carcharhinus leiodon, is one of the rarest whaler shark species of the genus Carcharhinus, previously known only from the holotype collected over 100 years ago from the Arabian Sea coast of Yemen. Recent market surveys in the Persian (Arabian) Gulf rediscovered 25 specimens (,2% of individual sharks recorded) in Kuwait, ,3000 km away from the type location. This study combined morphometric and molecular approaches to provide a detailed redescription of this species based on new material, as well as the first information on fresh colouration, size range and maturity. Sequences from two separate regions of the mitochondrial genome (COI and ND2) support the identity of C. leiodon as a distinct species, closely related to C. limbatus, C. amblyrhynchoides and C. tilstoni. Carcharhinus leiodon is superficially similar to, but clearly distinct from, C. melanopterus and C. amblyrhynchoides. The previously uncertain type locality of C. leiodon is considered to be correct, and the narrow range and unusual disjunct distribution, relatively rare for a marine carcharhinid, is discussed. The Kuwait population of C. leiodon, including juveniles, is subject to fisheries by-catch and is in an area of extensive habitat alteration. As a result, C. leiodon is considered vulnerable, requiring urgent conservation action.

Shark diversity in the Arabian/Persian Gulf higher than previously thought: insights based on species composition of shark landings in the United Arab Emirates

“…Similarly, reports of C. melanopterus from the Gulf are widespread, but few specimens have been confirmed (Gubanov and Schleib 1980;Bishop 2003). Moore et al (2011) suggested that this species may have been replaced by C. leiodon in shallow water habitats of the Gulf. However, in the UAE, C. melanopterus is common around many coastal and offshore islands (RWJ, personal observation) where fishing is prohibited, and the low number of sharks (n=38) recorded in this study may not reflect their abundance.…”

“…In our study, the C. limbatus and C. amblyrhynchoides species pair could not be convincingly differentiated by barcoding. Ward et al (2008) reported low COI sequence divergence and low bootstrap support for these species, and Moore et al (2011) stated that the COI gene was barely distinguishable between them. Similar outcomes were also reported for the closely related species C. plumbeus and C. altimus (Springer, 1950), leading to the conclusion that the COI barcode may not be suitable for discriminating among some closely related shark species, and that an additional marker with a higher rate of evolution would be necessary (Ward et al 2008).…”

A DNA Sequence–Based Approach To the Identification of Shark and Ray Species and Its Implications for Global Elasmobranch Diversity and Parasitology

“…While such barcode work will provide a useful parallel assessment of sequence variation, the fragment of COI used is both shorter (650 vs. 1044 bp) and more slowly evolving in chondrichthyans than is the NADH2 fragment (Moore et al, 2011). As such, we feel it may not be as useful for distinguishing among some closely related forms.…”

The importance of research and public opinion to conservation management of sharks and rays: a synthesis

“…Research is also needed on those species that are known from very few specimens, and are currently considered to have a very high risk of extinction. For example, Moore et al (2011) redescribed the poorly known smoothtooth blacktip shark (Carcharhinus leiodon) and provided a much clearer understanding of its distribution, biology, status and susceptibility to fisheries. Nowhere is this type of research more needed than in the deep sea (Kyne and Simpfendorfer 2010), from where the majority of new species are being described (Last and Stevens 2009).…”