Population genetics of four heavily exploited shark species around the Arabian Peninsula

Abstract

The northwestern Indian Ocean harbors a number of larger marine vertebrate taxa that warrant the investigation of genetic population structure given remarkable spatial heterogeneity in biological characteristics such as distribution, behavior, and morphology. Here, we investigate the genetic population structure of four commercially exploited shark species with different biological characteristics (Carcharhinus limbatus, Carcharhinus sorrah, Rhizoprionodon acutus, and Sphyrna lewini) between the Red Sea and all other water bodies surrounding the Arabian Peninsula. To assess intraspecific patterns of connectivity, we constructed statistical parsimony networks among haplotypes and estimated (1) population structure; and (2) time of most recent population expansion, based on mitochondrial control region DNA and a total of 20 microsatellites. Our analysis indicates that, even in smaller, less vagile shark species, there are no contemporary barriers to gene flow across the study region, while historical events, for example, Pleistocene glacial cycles, may have affected connectivity in C. sorrah and R. acutus. A parsimony network analysis provided evidence that Arabian S. lewini may represent a population segment that is distinct from other known stocks in the Indian Ocean, raising a new layer of conservation concern. Our results call for urgent regional cooperation to ensure the sustainable exploitation of sharks in the Arabian region.

Weak population structure of the Spot‐tail shark Carcharhinus sorrah and the Blacktip shark C. limbatus along the coasts of the Arabian Peninsula, Pakistan, and South Africa

“…Population genetic studies of sharks in the water bodies surrounding the Arabian Peninsula are scarce (Jabado & Spaet, ; Spaet, Thorrold, & Berumen, ), and so far, only one study has examined the population structure in four species of requiem sharks (Spaet, Jabado, Henderson, Moore, & Berumen, ). Given the limited data available on sharks in the region (Jabado & Spaet, ; Spaet, Cochran, & Berumen, ; Spaet, Thorrold, et al., ), increasing evidence of depleted shark populations (Clarke, Lea, & Ormond, ; Henderson, McIlwain, Al‐Oufi, & Al‐Sheili, ; Spaet, Nanninga, & Berumen, ), and alarming reports of local fishermen revealing declines in shark abundance of up to 80% (Jabado, Al Ghais, Hamza, & Henderson, ; Almojil, ), there is an urgent need to provide the basic science required for the conservation of these animals.…”

DNA barcoding reveals the diversity of sharks in Guyana coastal markets

“…altimus, C. limbatus (Valenciennes, 1839)/C. tilstoni (Whitley, 1950), cannot be uniquely diagnosed using barcoding methods (Wong et al, 2009;Spaet et al, 2015).…”

“…ND2, Control Region) to increase accuracy in species identification. For example, the co1 marker has been found to be of limited use for some closely-related species, particularly those within species complexes (Morgan et al, 2012;Spaet et al, 2015), and the 6 e170097 [6] incorporation of other markers with different gene histories can help identify closely-related taxa.…”

Extensive use of mesopelagic waters by a Scalloped hammerhead shark (Sphyrna lewini) in the Red Sea

“…Once brought alongside the vessel, the shark was measured for total length (TL) to the nearest cm and its sex visually determined by the absence of claspers (female). A small tissue sample was clipped from the left pectoral fin for genetic analysis [18]. One uniquely numbered external tag (FT-1 Dart Tag) was inserted in the basolateral dorsal musculature with a hollow canula (Floy Tag, Seattle, WA, USA).…”

“…Furthermore, S. lewini represents over 3% of all species traded in the Arabian Seas region [17]. At the same time, S. lewini populations in the western Indian Ocean appear fragmented with limited dispersal between the Arabian Seas region and other Indian Ocean regions [18]; yet, stock assessments and species-specific studies are missing in the area [19,20]. Gathering ecological information of movement data is a critical first step toward appropriate management strategies of shark species, and several studies have examined movements of S. lewini in different ocean systems (e.g., [21][22][23][24][25][26][27]).…”