Carcharhinus plumbeus ( Nardo, 1827 )

Carcharhinus plumbeus ( Nardo, 1827) View in CoL

IUCN standard name :: Sandbar Shark Fig. 7 View Figure 7 , Table 1 View Table 1

Material examined.

UPVMI 3119, 391 mm TL, male, Iloilo Fish Port Complex, Iloilo City, Philippines, 15 July 2020, coll. R. Cabebe-Barnuevo, E. Delloro Jr., D. Mediodia, E. Obar, and N. Ylaron. UPVMI 3120, 363 mm TL, male, same data as preceding. UPVMI 3183, male, 370 mm TL, same data as preceding.

Morphological description.

Body moderately small and cylindrical. Head slightly depressed. Eyes large and rounded, spiracles absent. Snout short and relatively blunt; length of snout shorter than mouth width (8 % vs. 9 % TL, respectively). Mouth short and transversely curved. Nostril long with short nasal flap; nostril distance shorter than mouth width (6 % vs. 9 % TL, respectively). Teeth on upper jaw broadly triangular; teeth on lower jaw still not visible. First dorsal fin tall, height more than half of predorsal length (16 % vs. 27 % TL, respectively), originating over pectoral-fin insertion; second dorsal fin considerably smaller than first dorsal fin, originating slightly anterior to anal-fin insertion. Anal fin small, considerably same size with second dorsal fin; posterior margin concave. Pectoral fin large; posterior margin concave. Pelvic fin relatively smaller than pectoral fin. Caudal fin relatively long; posterior tip of upper lobe slightly narrow; lower lobe distinct, slightly triangular; ventral notch located near tip of upper lobe. Interdorsal-fin ridge present. Precaudal pits transverse.

Color of fresh specimen. Body and head dark gray; underside white; fins plain with dusky tip.

Color of preserved specimen. Body, head, and fins plain gray; underside portion of body white.

Distribution.

Wide-ranging in tropical through warm temperate areas, including Mediterranean Sea, but possibly not eastern Pacific. Extends from western central Pacific to Hawaii ( Compagno and Niem 1998 c), and across western Indian Ocean from South Africa (eastern Cape), to the Red Sea, Gulf of Oman, Persian / Arabian Gulf, Pakistan, India, Socotra, Madagascar, Seychelles, Mauritius, and Lakshadweep ( Winton and Ebert 2022).

DNA barcode.

COI sequences of 617 bp were submitted to GenBank with accession numbers OR 614473 ( UPVMI 3119) and OR 614471 ( UPVMI 3120).

Conservation status.

Endangered

Remarks.

This is the first verified report of Carcharhinus plumbeus from Philippine waters, as previous studies only reported a possible set of jaws that could not be confirmed ( Compagno et al. 2005). Globally, populations of C. plumbeus have declined by more than 50 % due to fisheries overexploitation and coastal habitat degradation ( Rigby et al. 2021). The confirmed presence of small C. plumbeus individuals (smaller than published size-at-birth estimates; Rigby et al. 2021) in Iloilo’s largest fish market indicates an urgent need to enact monitoring and management policies. The largest known specimen of C. plumbeus measures 3 m TL ( Soufi-Kechaou et al. 2018). Typically, this species is found at depths ranging from 20–60 m, although it can occasionally inhabit deeper waters up to 280 m ( Compagno and Niem 1998 c; Last et al. 2010).

The specimens were identified as C. plumbeus based on several morphological characteristics, including the presence of an interdorsal ridge, triangular upper jaw teeth, and first dorsal fin originating above pectoral fin, with its height exceeding half of the predorsal length (16 % vs. 27 % of TL, respectively). Serena (2005) noted that C. plumbeus is frequently confused with Carcharhinus altimus ( Springer, 1950) and Carcharhinus obscurus ( Lesueur, 1818) . These three species exhibit similarities such as rounded snout, serrated upper teeth, presence of an interdorsal ridge, and fins with plain or dusky tips rather than conspicuously black-tipped fins. However, C. plumbeus is distinguished from these two species by its tall first dorsal fin (vs. short dorsal-fin height, less than half of predorsal length) ( Compagno and Niem 1998 c). Additionally, C. plumbeus can be distinguished from C. altimus by having a short snout, which is shorter than the mouth width (8 % vs. 9 % TL, respectively) (vs. long snout with a length equal to or greater than the mouth width in C. altimus ). Phylogenetic analysis further supports this identification, showing that C. plumbeus is closely related to C. altimus and C. obscurus , with these three species forming a distinct clade separate from Carcharhinus sorrah ( Valenciennes, 1839) (Fig. 3 View Figure 3 ). Moreover, COI barcoding results confirm the identification of the Philippine specimens as C. plumbeus , as they cluster with other sequences of C. plumbeus . The extended distribution in Philippine waters confirmed by this study will support efforts to assess and protect this species.