Sandbar Shark

fieldmarks: A medium-sized gray shark with short rounded snout, an extremely tall triangular first dorsal fin with its origin over or anterior to the pectoral insertions, broad- and high-cusped, triangular serrated upper teeth without cusplets, usually 14/13-14 rows of anterolateral teeth, an interdorsal ridge, large pectoral fins, a moderately large dorsal with a short rear tip, and no conspicuous markings on fins. Medium to large, fairly stocky sharks (up to about 2.4 m but mostly smaller) with snout short and broadly rounded or broadly parabolic, internarial width 0.9 to 1.3 in preoral length. Eyes circular and moderately large, length 1.7-2.9%TL. Nostrils with very short, low, poorly developed anterior nasal flaps. Upper labial furrows short and inconspicuous. Hyomandibular line of pores just behind mouth corners not conspicuously enlarged. Gill slits short, 3rd 2.4-3.6% TL and less than a third of first dorsal base. Usually 14/13-14 rows of anteroposterior teeth in each jaw half but varying from 14-15/12-15; upper teeth with broadly triangular, strongly serrated, semierect to slightly oblique cusps merging smoothly into crown feet with slightly coarser serrations but no cusplets; lower teeth with erect, narrow serrated cusps and transverse roots. A narrow interdorsal ridge present. Pectoral fins large, semifalcate, with narrowly rounded or pointed apices, length of anterior margins about 17 to 22%TL. First dorsal fin very large and semifalcate, with pointed or narrowly rounded apex and posterior margin curving ventrally from fin apex; origin of first dorsal fin over or slightly anterior to pectoral insertions; inner margin of first dorsal moderately long, 2/5 of dorsal base or slightly less. Second dorsal fin moderately high, height 2.1 to 3.5% TL, inner margin short and 1.0 to 1.6 times height; origin of second dorsal over or slightly anterior to anal origin. 152-189 total vertebral centra, 82-97 precaudal centra. Colour gray-brown above, white below; tips and posterior edges of fins often dusky, but no conspicuous markings; an inconspicuous white band on flank.

Maximum possibly to 3 m but otherwise to 239 cm or less for adults; males maturing at 131 to 178 cm and reaching 224 cm; females maturing at 144 to 183 cm and reaching 234 cm; size at birth 56 to 75 cm.

An abundant, inshore and offshore, coastal-pelagic shark of temperate and tropical waters, found on continental and insular shelves and in deep water adjacent to them, and oceanic banks;common at bay mouths, in harbours, inside shallow muddy or sandy bays, and at river mouths, but tends to avoid sandy beaches and the surf zone, coral reefs and rough bottom, and the surface.Depths range from the intertidal in water barely deep enough to cover it to 280 m. Although common in inshore environments, it does not ascend rivers into fresh water. It favours the bottom, and normally is not seen at the surface unless travelling in water so shallow that its large first dorsal fin comes out of the water.As with several other wide-ranging carcharhinids this species has a number of allopatric populations in different areas. In the Western Atlantic Springer (1960) suggested that there are two stocks or subpopulations of sandbar sharks, a northern major one from the US Atlantic seaboard to the Gulf of Mexico and the eastern Caribbean, and a minor South American one from Trinidad eastwards and southwards to Brazil. Although this remains to be proven by tagging, Springer hypothesized that the separate Eastern Atlantic population of this shark was capable of contributing to the South American population via migration with the equatorial current across the Atlantic. [more...] Preferred temperatures in shallow water off Madagascar are 23 to 24°C; off the Hawaiian Islands these sharks occur in waters 24 to 27°C. Viviparous, with a yolk-sac placenta; number of young 1 to 14 per litter, with 5 to 12 common. Litter size varies directly with size of the mother, and in populations with smaller adults the litter size averages smaller. The size of young at birth varies considerably among different allopatric populations of this shark, including adjacent ones in the Western Atlantic, as does the size attained by adults. In this shark as in many other carcharhinids the size range of adults is relatively narrow, indicating virtually determinate growth after maturity. The gestation period is estimated as 8 to 12 months, commonly 9 months off Florida, and 11 to 12 months off South Africa and in the South China Sea. [more...] In captivity these sharks show growth rates that suggest maturation in as little as three years, but other estimates based on tooth replacement suggests 10 years for males and 13 for females. Springer (1960) suspected that sandbar sharks may mature in only two years, but on little real evidence. Presumably this is somewhere between 3 and 10 years.The sandbar shark is primarily a predator on relatively small bottom fishes, with some molluscs and crustaceans taken. [more...] It does not consume garbage and mammalian carrion as a rule, unlike some other members of its genus. Evidence from fisheries indicates that very fresh fish bait is greatly preferred by these sharks to stale or even fresh-frozen fish, and fish greatly preferred to mammalian meat. These sharks feed by day and night, more actively at night. It is thought that this shark is far more successful in obtaining a regular supply of food than larger carcharhinids such as Galeocerdo cuvier, Carcharhinus leucas and Carcharhinus obscurus ; this is reflected in greater number of sandbar sharks with full or nearly full stomachs, and liver weight, which shows much less fluctuation in sandbar sharks than in the three larger species. Data from captive individuals suggests that digestion is relatively rapid, and prey is largely digested after two days.It is thought that adult sandbar sharks are rarely eaten by other larger sharks and may be difficult prey for them (with the likely exception of the great white shark, which is known to eat adults of this species), but that the young are readily taken by other sharks, particularly the bull and tiger sharks, which feed on them in inshore areas.

This is an abundant inshore and offshore species where it occurs, and forms an important object of fisheries especially in the western North Atlantic, eastern North Atlantic, and South China Sea. USA have reported to FAO catch statistics for this species in Northwest Atlantic in 1988 (2 t) and 1992-1995 (55, 31, 21 and 1 t, respectively). No catch reported for this species to FAO for 1999 It is caught with longlines, hooks and lines, and set bottom nets and is also fished with rod and reel by sports anglers as a game fish. It is utilized fresh, fresh-frozen, smoked and dried salted for human consumption; the hides are prized for leather and other products; the fins are prepared as the base for shark-fin soup; and the liver is extracted for oil (rich in vitamins). Impact of fisheries The sandbar shark is taken commercially in coastal fisheries throughout its range and is also an important part of some sport fisheries. This species is very common in the small-scale shark fisheries of Eastern México where adults and subadults are commonly caught (Bonfil 1997). Sandbar sharks are also taken in the fisheries of Taiwan and Western Australia (Bonfil 1994), as well as in the Arabian Sea (Sivasubramaniam 1992). However, there are no abundance indices for any of these fisheries. Sandbar sharks are the second preferred shark in sport fisheries in the East Coast of the US (Hoff and Musick 1990) where some 750,000 individuals are killed annually (National Marine Fisheries Service 1993, cited by Musick in press). Because of the high quality of its flesh and its large fins, this is the most important commercial species in the shark fishery of the southeastern United States where an average of 550 t/y were taken in 1992-1995 (Rose 1998). Sandbar sharks have suffered a decline similar to that of dusky sharks in the US East Coast. Musick et al. (1993) documented a considerable drop in CPUE of the sandbar shark off Virginia. Ulrich (1996, cited by Castro et al. in press) reports a dramatic decline of sandbar shark abundance off South Carolina, from 4.73 sharks /100 hooks in 1983-84, to 0.39 sharks /100 hooks in 1994-95. Abundance indices from the US sport fishery of Virginia-Massachusetts decreased sharply from 1988 to 1996 and started rising only in 1997 (Brown 1998). A management plan for this and other species is in place in the US Atlantic since 1993. Recent strong reductions in the TAC seem to begin showing their positive effect as 4 out of 5 sandbar abundance indices show increasing trends since 1993 (Anon. 1998). Cliffet al. (1988) report that catch rates of sandbar sharks in the beach protection programme of Natal dropped from 2.3 to 0.7 sharks/km-net/year from the 1966-72 to the 1978-87 period. However, these authors point that factors other than net-induced mortality must be responsible for the change given the small netting effort in comparison to the overall range of the sandbar shark population in the region. Conservation Status : The sandbar shark has a very low intrinsic rebound potential (Smith et al. 1998) and can be easily depleted when fished carelessly. The IUCN Red List classifies sandbar sharks as Lower Risk/Near Threatened at the world level and the stocks in US waters of the Atlantic and Gulf of México as Lower Risk/Conservation Dependent (Camhiet al. 1998). Mooney-Seus and Stone (1996) consider sandbar sharks as Severely Reduced in US Atlantic waters and Data Deficient in the rest of the Atlantic and Pacific. Newborns and juveniles inhabit temperate coastal lagoons, thus habitat degradation and human encroachment further threaten some stocks (i.e. US Atlantic coast). Unrestricted sport and commercial exploitation through the 1970s and 1980s brought down the stocks of the US Atlantic coast to very low levels. Conservative catch quotas introduced through a management plan for the recovery of large coastal sharks in 1993 were further reduced in 1997 due to concerns over the recovery of sandbar sharks (Camhi et al. 1998). The abundance indices for this species show a slow increase since management came about but the stock is still a long way from recovery. The Western Australia commercial shark fishery exploits the younger age classes of the local sandbar shark population (Simpfendorfer 1998), but the breeding part of this stock is under protection through a no-take MPA (see dusky shark account). Additional information from IUCN database Additional information from CITESdatabase