(Smale, M.J. (1991). The species grows very slowly; it matures in 17 … The mouth has very short, subtle furrows at the corners and contains 13-15 (typically 14) tooth rows on either side of both jaws. This would be advantageous given the sharks’ itinerant natures and low natural abundance, which would make encounters with suitable mates infrequent and unpredictable. Newborn and juvenile sharks subsist mainly on small pelagic prey such as sardines and squid; older sharks over 2 m (6.6 ft) long broaden their diets to include larger bony and cartilaginous fishes. Dusky sharks also carry the copepods Alebion sp., Pandarus cranchii, P. sinuatus, and P. smithii. Current status The current status of dusky sharks in South African waters is not known. Some research suggests this could be due to their nee to conserve energy. Juveniles spend spring and summer in the surf zone and fall and winter in offshore waters, and as they approach 7.2 feet in length begin to conduct a north-south migration between KwaZulu-Natal in the winter and the Western Cape in summer. They are blue-grey in color which fades into its creamy white underbelly. (March 26, 2009). Carcharhinus obscurella Deng, Xiong & Zhan, 1981 These sharks are viviparous, ie they produce live young. This shark was once one of the most important species in the Florida trophy shark tournaments, before the population collapsed.[51]. Dusky Shark Recorded Attacks on Humans: The Dusky shark is potentially dangerous to humans. Females are mature when they are 9 ft (2.8 m) long and have litters of about 10 pups which are roughly 3 ft (95 cm) long each. The nostrils are preceded by barely developed flaps of skin. Demographic models suggest that the fishery is sustainable, provided that the mortality rate of sharks over 2 m (6.6 ft) long is under 4%. Here in Florida it is typical to see Silkies, Sandbar sharks and Dusky sharks together, and on occasion, we have seen Oceanic Whitetips with the. A low dorsal ridge is present between the dorsal fins. Demographic, Distribution, Habitat, Environment and Range: The Dusky shark can be found worldwide in warm-temperate tropical waters. Galeolamna eblis Whitley, 1944 [52] The maximum lifespan is believed to be 40–50 years or more. They also carry the leech Stibarobdella macrothela. The five pairs of gill slits are fairly long.[20]. Off KwaZulu-Natal, the use of shark nets to protect beaches has reduced the populations of these larger predators, leading to a studied increase in the number of juvenile Dusky sharks (a phenomenon called “predator release”). These nurseries offer their pups abundant food supplies and shelter from predation. This is more noticeable in juveniles. Off South Africa, young males and females over 3.0 feet long scatter southward and northward respectively from the nursery area off KwaZulu-Natal; they join the adults several years later by a yet-unidentified route. The dusky shark is regarded as potentially dangerous to humans due to its large size, but there are few attacks attributable to it. Classification: Order The Dusky shark does however prefer hunting towards the bottom. It prefers water temperatures of 19–28 °C (66–82 °F), and avoids areas of low salinity such as estuaries. This page was last edited on 24 October 2020, at 18:02. 8. The known invertebrates in their diet are cephalopods, decapod crustaceans, sea stars and barnacles. [7], Teeth belonging to the dusky shark are fairly well represented in the fossil record, though assigning Carcharhinus teeth to species can be problematic. [20] This species is bronzy to bluish gray above and white below, which extends onto the flanks as a faint lighter stripe. The fins, mainly the underside of the pectoral fins and the lower caudal fin lobe darken towards the tips. In the eastern Atlantic Ocean, it has been reported from the western and central Mediterranean Sea, the Canary Islands, Cape Verde, Senegal, Sierra Leone, and possibly elsewhere including Portugal, Spain, Morocco, and Madeira. [53] However, attacks attributed to this species off Bermuda and other islands were probably in reality caused by Galapagos sharks. Pregnant and post-partum females do not join, possibly because the energy cost of gestation leaves them unable to pursue such swift prey. [36], Full-grown dusky sharks have no significant natural predators. Lesueur did not designate a type specimen, though he was presumably working from a shark caught in North American waters. The Dusky shark is one of the most desirable species for shark fin trade, as its fins are large and contain a high number of internal rays. In 2005, North Carolina implemented a time/area closure to reduce the impact of recreational fishing. Lifeguards close Town Beach this morning Births may occur over a long time span of several months in pupping areas, and have been reported as occurring from late winter to summer. Dusky sharks have a color of Gray or beige. (2009). Check out our videos with these species together! Very rarely, the largest dusky sharks may also consume sea turtles, marine mammals (mainly as carrion), and human refuse. Cartilaginous fishes, mainly skates and their egg cases, are the second-most important dietary component, while the lady crab (Ovalipes ocellatus) is also a relatively significant food source. [51] Various studies have found growth rates to be largely similar across geographical regions and between sexes. This doesn’t seem to associate with the size of the female. [22] The dermal denticles are diamond-shaped and closely set, each bearing five horizontal ridges leading to teeth on the posterior margin. and the Dusky sharks also carry the sea lamprey Petromyzon marinus, and are the hose of the sharksucker Echeneis naucrates. Teeth and Jaw: The mouth of a Dusky shark has very short, subtle furrows at the corners and contains 13-15 (normally 14) tooth rows on either side of both jaws. French naturalist Charles Alexandre Lesueur published the first scientific description of the dusky shark in an 1818 issue of Journal of the Academy of Natural Sciences of Philadelphia. 8. Litter size ranges from 3 to 16, with 6 to 12 being typical, and does not correlate with female size. [9] Dusky shark teeth have also been recovered from the vicinity of two baleen whales in North Carolina, one preserved in Goose Creek Limestone dating to the Late Pliocene (c. 3.5 Ma), and the other in mud dating to the Pleistocene-Holocene (c. 12,000 years ago). On occasion, the larger Dusky sharks will eat sea turtles, marine mammals (mainly as carrion), and human refuse. [42][43] The run of the southern African pilchard (Sardinops sagax), occurring off the eastern coast of South Africa every winter, is attended by medium and large-sized dusky sharks. Carcharias macrurus Ramsay & Ogilby, 1887 This is the highest figure thus far measured from any shark, though it also reflects the concentration of force at the tooth tip. [8], The range of the dusky shark extends worldwide, albeit discontinuously, in tropical and warm-temperate waters. Based on a study in 1993 by Pratt, females are capable of storing masses of sperm, possibly from multiple males, for months to years within their nidamental glands (an organ that secretes egg cases). The dusky shark attains large sizes, reaching 360 cm Total Length (TL) (Castro 1993). In addition, juveniles spend spring and summer in the surf zone and fall and winter in offshore waters, and as they approach 2.2 m (7.2 ft) in length begin to conduct a north-south migration between KwaZulu-Natal in the winter and the Western Cape in summer. The meat is sold fresh, frozen, dried and salted, or smoked, the skin is made into leather, and the liver oil is processed for vitamins. [7][20] Females grow larger than males. [1], One of the largest members of its genus, the dusky shark commonly reaches a length of 3.2 m (10 ft) and a weight of 160–180 kg (350–400 lb); the maximum recorded length and weight are 4.2 m (14 ft) and 347 kg (765 lb) respectively. Larger Dusky sharks, over 9.2 feet long, migrate as far as southern Mozambique. A dusky whaler litter contains 3–14 pups,2 possibly more, born at about 70–100 cm total length. First dorsal fin slopes2. Live shortfin makos must be released unharmed to the water in Commonwealth managed fisheries operating off South Australia (outside 3 nm). Mostly medium and large Dusky sharks will be seen. [45], With a gestation period estimated at up to 22–24 months and a one-year resting period between pregnancies, female dusky sharks bear at most one litter of young every three years. Based on our observational studies here with Rhonda, her behavior may have been influenced by external factors. The fins of young dusky sharks are usually darker than those older sharks. Adults are often found following ships far from land, such as in the Agulhas Current. With a gestation period estimated at up to 22–24 months and a one-year resting period between pregnancies, female Dusky sharks have at most one litter of young every three years. But sometimes rarely off southern California; common in tropics. In 2005, North Carolina implemented a time/area closure to reduce the impact of recreational fishing. Their snout is a little shorter than most others and they have a low interdorsal ridge. To support conservation efforts, molecular techniques using polymerase chain reaction (PCR) have been developed that can identify whether marketed shark parts (e.g. The International Union for Conservation of Nature (IUCN) has assessed this species as Endangered worldwide. [19] A tracking study off the mouth of the Cape Fear River in North Carolina reported an average swimming speed of 0.8 km/h (0.50 mph). Females grow larger than males. Marine Biotechnology.). Diet: The Dusky shark will eat a variety of food, and from all water column levels; it surely isn’t picky. Gestation period of ~ 16 months (Ref.58048). Birth may occur over a long time span of several months in a given region, and has been reported as occurring from late winter to summer. The reproductive cycle of the dusky shark is three years with a gestation period of approximately two years and a one year resting period (Romine et … They also eat tuna and mackerel, billfish, jacks, needlefish, flyingfish, threadfins, hairtails, lanternfish, and lancetfish. About 1-year gestation period with litter size of 60-100 pups; newborn length doubles in 6 months and adults grow 0-9 cm/year. Dusky Sharks give birth to “litters” of pups, anywhere from 3-14 at a time! They average 8 pups instead of 10 pups. They average 8 pups instead of 10 pups. Endangered Species Act (ESA). I’m a big guy (reaching up to 400 lbs! [13] Teeth dating to the Late Miocene or Early Pliocene (11.6-3.6 Ma) are abundant in the Yorktown Formation and the Pungo River, North Carolina, and from the Chesapeake Bay region; these teeth differ slightly from the modern dusky shark, and have often been misidentified as belonging to the oceanic whitetip shark (C. The first dorsal fin is of moderate size and somewhat falcate, with a pointed apex and a strongly concave rear margin; its origin lies over the pectoral fin free rear tips. There may be no correlation between maternal size and litter size in this shark, unlike some other species of Carcharhinus. There is evidence that females can determine the size at which their pups are born, so as to improve their chances of survival across better or worse environmental conditions. Size at birth between 70 and 100 cm. For both the dusky and spinner shark, there was a linear increase in near-term pup mass with month, which may indicate variable parturition strategies and/or that carcharhinids are able to adjust the length of the gestation period. Here in Jupiter that is true, and we see the three species together often. Newborn and juvenile sharks subsist mainly on small pelagic prey such as sardines and squid; older sharks over 6.6 feet long will start to eat larger bony and cartilaginous fishes. Dusky sharks in the western Atlantic seem to produce slightly smaller litters than those from the southeastern Atlantic. The nostrils have small skin flaps, and they have circular eyes that are medium in size with nictitating membranes. There have been some accounts in Madeira, Portugal, Spain, and Morocco. 75154). You can find me in tropical and subtropical oceans around the world, and I make long seasonal migrations all the way from the Equator to the Poles. In the Indian Ocean, it is found off South Africa, Mozambique, and Madagascar, with sporadic records in the Arabian Sea, the Bay of Bengal, and perhaps the Red Sea. [20] Major predators of young sharks include the ragged tooth shark (Carcharias taurus), the great white shark (Carcharodon carcharias), the bull shark (C. leucas), and the tiger shark (Galeocerdo cuvier). Because of its slow reproductive rate, the dusky shark is very vulnerable to human-caused population depletion. The medium-sized, circular eyes are equipped with nictitating membranes (protective third eyelids). I’m worrie… In the surf zone, dusky sharks swim to a depth of 573m (1,879 ft). Dusky sharks in the western Atlantic seem to produce slightly smaller litters than those from the southeastern Atlantic. This doesn’t seem to associate with the size of the female. Adult dusky sharks have a broad and varied diet, consisting mostly of bony fishes, sharks and rays, and cephalopods, but also occasionally crustaceans, sea stars, bryozoans, sea turtles, marine mammals, carrion, and garbage. The coloration quickly fades to a dull gray after death. From our personal experience, on one occasion, a Dusky shark off the coast of Texas at an oil rig behaved in an inquisitive manner, swimming in and out of a group of divers cautiously, then after about 15 minutes, swam off. Speed: A tracking study off the mouth of the Cape Fear River in North Carolina reported an average swimming speed of a Dusky shark at 0.50 mph. In 1997, the dusky shark was identified as a Species of Concern by the NMFS, meaning that it warranted conservation concern but there was insufficient information for listing on the U.S. [51], In addition to commercial shark fisheries, dusky sharks are also caught as bycatch on longlines meant for tuna and swordfish (and usually kept for its valuable fins), and by recreational fishers. In addition, some 2,000 dusky sharks were caught by recreational fishers in 2003 despite the ban. Some of these nursery areas are known along the coasts of KwaZulu-Natal, southwestern Australia, western Baja California, and the eastern United States from New Jersey to North Carolina. South African Journal of Marine Science.). In South Africa, there is no trace of seasonality. Reported up to 290 cm (9.7 ft). Distinct pairing with embrace. It has a very wide distribution in tropical and warm temperate waters. Little is known or studied about its behavior towards humans underwater. Newborn Dusky sharks measure between 2.3–3.3 feet long. The Sardine run is full of energy from the smallest being to the largest. Head: The Dusky shark has a broadly rounded snout no longer than the width of the mouth. Females also provision their young with energy reserves, stored in a liver that comprises one-fifth of the pup’s weight, which sustains the newborn until it learns to hunt for itself. The second dorsal fin is much smaller and is positioned about opposite the anal fin. [54] Commercial and recreational retention of dusky sharks was prohibited in 1998, but this has been of limited effectiveness due to high bycatch mortality on multi-species gear. (III) and Grace, M.A. Behavioral Traits, Sensing and Intelligence: Dense aggregations of young sharks, forming in response to feeding opportunities, have been documented in the Indian Ocean. However, pregnant females, or post-partum females do not participate. Dusky sharks are a part of the annual Sardine Run off the eastern coast of South Africa every winter. The large pectoral fins measure around one-fifth as long as the body, and have a falcate shape tapering to a point. Garrick, J.A.f. [4][43] These nursery areas are known along the coasts of KwaZulu-Natal, southwestern Australia, western Baja California, and the eastern United States from New Jersey to North Carolina. (Pank, M.; Stanhope, M.; Natanson, L.; Kohler, N. & Shivji, M. (May 2001). On another occasion here in Jupiter, a migratory returning resident Dusky shark local call Rhonda, seems to always hold interest in divers, and has a hard time finding any other interest when divers are present. (April 20, 2009). [39] One South African study reported that 0.2% of the sharks examined had preyed upon bottlenose dolphins (Tursiops truncatus). [20] Depending on region, birthing may occur throughout the year or over a span of several months: newborn sharks have been reported from late winter to summer in the northwestern Atlantic, in summer and fall off Western Australia, and throughout the year with a peak in fall off southern Africa. ), but despite our mighty reputation, sharks are under threat from overfishing (including when we’re accidentally caught as bycatch or collected for shark fin soup), pollution and habitat loss. Aesthetic Identification: One of the first things you will notice about the Dusky shark is its slender, streamlined body. "Occurrence and feeding of three shark species, "The storage of spermatozoa in the oviducal glands of western North Atlantic sharks". Gestation period of ~ 16 months (Ref.58048). Dusky sharks along both coasts of North America shift northward with warmer summer temperatures, and withdrawal back towards the equator in winter. Dusky Shark (Carcharhinus obscurus) ... and lowest litter rates of all sharks. Humans use shark nets to protect beaches in South Africa and Australia, and they entangle adult and larger juvenile Dusky sharks in large quantities. Age at maturity about 6 years, expected life span at least 18 years. Populations migrate seasonally towards the poles in the summer and towards the equator in the winter, traveling hundreds to thousands of kilometers. Phylogenetic relationships of the dusky shark, based on allozyme sequences. Prionodon obvelatus Valenciennes, 1844 Dusky Sharks give birth to “litters” of pups, anywhere from 3-14 at a time! Few Dusky shark attacks are documented, but it is considered dangerous. The preferred temperature is between 66-82 degrees F. They do not care for low salinity waterways. One of the largest members of its genus, the silky shark commonly reaches a length of 2.5 m (8.2 ft), with a maximum recorded length and weight of 3.5 m (11 ft) and 346 kg (763 lb), respectively. Gestation period of ~ 16 months. It is also esteemed by recreational fishers. The Dusky Whaler is a 'typical', streamlined, grey-coloured shark. carcharhinid,the dusky shark [Carcharhinus obscurus (LeSu-eur, 1818)], was selected as a test species. Mating occurs during spring in the northwestern Atlantic, while there appears to be no reproductive seasonality in other regions such as off South Africa. As an apex predator positioned at the highest level of the trophic web, the dusky shark is generally less abundant than other sharks that share its range. [1][2] Mitochondrial DNA and microsatellite evidence suggest that Indonesian and Australian sharks represent distinct populations. One interesting theory suggests that female Dusky sharks can determine the size which their pups are born, so as to improve their chances of survival across better or worse environmental conditions. and produce litters of between 3-16 pups. Dusky sharks also eat demersal fishes, including mullets, porgies, grunts, and flatheads, eels, lizardfish, cusk eels, gurnards, and flatfish. The dusky shark is assessed by the International Union for the Conservation of Nature (IUCN) as “Vulnerable A2bd” worldwide, with populations in the Northwest Atlantic and Gulf of Mexico being considered “Endangered” (Musick et The Dusky shark is commonly mistaken, and therefore some accounts of Dusky sharks from the northeastern and eastern central Atlantic, and around tropical islands, may be of Galapagos sharks. The southwestern Australian fishery began in the 1940s and expanded in the 1970s to yield 500–600 tons per year. The Dusky shark has been recorded as deep as 1,300 feet. The dusky shark (Carcharhinus obscurus) is a species of requiem shark, in the family Carcharhinidae, occurring in tropical and warm-temperate continental seas worldwide. "Dusky Sharks While Filming Bluewater Savages" footage of dusky sharks and an underwater videography team. It has a slender, streamlined body and can be identified by its short round snout, long sickle-shaped pectoral fins, ridge between the first and second dorsal fins, and faintly marked fins. Due to these actions, the juvenile Dusky sharks have decimated populations of small bony fishes, with negative consequences for the biodiversity of the local ecosystem. 2005). The fins, particularly the underside of the pectoral fins and the lower caudal fin lobe) darken towards the tips; this is more obvious in juveniles. In South African waters birth may occur year-round with an increase in autumn. Sharks of the genus, Hoffmayer, E.R., Franks, J.S., Driggers, W.B. This would be advantageous given the sharks' itinerant natures and low natural abundance, which would make encounters with suitable mates infrequent and unpredictable. [23][38] A large individual can consume over a tenth of its body weight at a single sitting. [7] Dusky sharks are taken by targeted commercial fisheries operating off eastern North America, southwestern Australia, and eastern South Africa using multi-species longlines and gillnets. The maximum lifespan of a Dusky shark is believed to be 40–50 years or more. For the dusky shark, there was a trade-off between increasing litter size and near- term pup mass in support of optimal offspring size theory. "Age and growth estimates for the dusky shark, "The condition conundrum: application of multiple condition indices to the dusky shark. [51], The dusky shark is considered to be potentially dangerous to humans because of its large size, though little is known of how it behaves towards people underwater. In the western Atlantic Ocean, it is found from Massachusetts and the Georges Bank to southern Brazil, including Cuba and the Bahamas. Sampson said with the prohibition on keeping any dusky shark regardless of size failing, NMFS is now exploring a blanket minimum size increase … Data on reproduction suggested a 3-year reproductive cycle consisting of a 2-year gestation period and a 1-year resting period. Here in Florida it is typical to see Silkies, Sandbar sharks and Dusky sharks together, and on occasion, we have seen Oceanic Whitetips with the. The average litter size is 10, with litters ranging between 2 and 14 pups (Last and Stevens, 2009; Romine et al., 2009). [5] However, high concentrations of individuals, especially juveniles, can be found at particular locations. Depending on region, birthing may happen throughout the year or over a span of several months: newborn sharks have been reported from late winter to summer in the northwestern Atlantic, in summer and fall off Western Australia, and throughout the year with a peak in fall off southern Africa. Sharks along both coasts of North America shift northward with warmer summer temperatures, and retreat back towards the equator in winter. With a gestation period estimated at up to 22–24 months and a one-year resting period between pregnancies, female dusky sharks bear at most one litter of young every three years. Off Western Australia, adult and juvenile Dusky sharks migrate towards the coast in summer and fall. Naylor was able to further resolve the interrelationships of the "ridge-backed" branch of Carcharhinus, finding that the dusky shark, Galapagos shark, oceanic whitetip shark, and blue shark (Prionace glauca) comprise its most derived clade. Size Range: Common length — 70–400cm; Size limits on takes: Maximum size 150cm; or interdorsal length 60cm max. [1], The known diet of the dusky shark encompasses pelagic fishes, including herring and anchovies, tuna and mackerel, billfish, jacks, needlefish and flyingfish, threadfins, hairtails, lancetfish, and lanternfish; demersal fishes, including mullets, porgies, grunts, and flatheads, eels, lizardfish, cusk eels, gurnards, and flatfish; reef fishes, including barracudas, goatfish, spadefish, groupers, scorpionfish, and porcupinefish; cartilaginous fishes, including dogfish, sawsharks, angel sharks, catsharks, thresher sharks, smoothhounds, smaller requiem sharks, sawfish, guitarfish, skates, stingrays, and butterfly rays; and invertebrates, including cephalopods, decapod crustaceans, barnacles, and sea stars. For example, for viviparous sharks, litter size ranges from six for the basking shark to 82 for the blue shark, Prionace glauca. Heim, B. and Bourdon, J. [25] Known parasites of this species include the tapeworms Anthobothrium laciniatum,[26] Dasyrhynchus pacificus,[27] Platybothrium kirstenae,[28] Floriceps saccatus,[29] Tentacularia coryphaenae,[30] and Triloculatum triloculatum,[31] the monogeneans Dermophthirius carcharhini[32] and Loimos salpinggoides,[33] the leech Stibarobdella macrothela,[34] the copepods Alebion sp., Pandarus cranchii,[35] P. sinuatus,[20] and P. smithii, the praniza larvae of gnathiid isopods,[35] and the sea lamprey (Petromyzon marinus). Occurs on the continental shelf and slope (Ref. It has 5 pairs of long gill slits. It normally eats small fish (like sardines), large fish (like tuna), flatfish, other sharks, and eels. The annual estimated growth rate is 3.1–4.3 inches over the first five years of its life. The first dorsal fin is of moderate size and somewhat falcate, with a pointed apex and a strongly concave rear margin; its origin lies over the pectoral fin free rear tips. The litter size of Dusky shark’s ranges from 3 to 16, with 6 to 12 being the average. Dusky sharks look a lot like your "typical" shark in that they are almost torpedo-shaped. For aplaental viviparous sharks, litter size ranges from two for the bigeye and pelagic thresher shark [21, 22] to more than 300 for the whale shark (S1 Table). Late term females lack a large yolky ova; this is one reason why they have to wait a year to mate again (Romine, 2009). This is the highest figure so far measured from any shark, though it also reflects the concentration of force at the tooth tip. I’m a big ocean predator who loves to travel! Tracking. They have a maximum size of between 2.5 metre to 4 metres in length depending on the species, and are often grey to dusky bronze in colour. [4] Adults are often found following ships far from land, such as in the Agulhas Current. Carcharhinus iranzae Fourmanoir, 1961 2 (Musick et al. [5], The dusky shark is one of the most sought-after species for shark fin trade, as its fins are large and contain a high number of internal rays (ceratotrichia). Viviparous, with a yolk-sac placenta, litter size 3-14 pups ; 70-100 cm at birth. [4][18], The dusky shark is nomadic and strongly migratory, undertaking recorded movements of up to 3,800 km (2,400 mi); adults generally move longer distances than juveniles. “Rapid and Simultaneous Identification of Body Parts from the Morphologically Similar Sharks Carcharhinus obscurus and Carcharhinus plumbeus (Carcharhinidae) Using Multiplex PCR“. In the eastern Atlantic Ocean, it has been reported from the western and central Mediterranean Sea, the Canary Islands, Cape Verde, Sierra Leone, and Senegal. Denticles: The dermal denticles of a Dusky shark are diamond-shaped and closely set, each has five horizontal ridges leading to teeth on the posterior margin. 2007 at 4; Morgan 2010 at 1) The international shark fin trade, an estimated $73 billion market, threatens the dusky shark’s continued existence. At birth, dusky sharks are about a length of 70–100 cm (27.6-39.3 in). All Rights Reserved. [5] As of 2009, the International Shark Attack File lists it as responsible for six attacks on people and boats, three of them unprovoked and one fatal. Viviparous, with a yolk-sac placenta, litter size 3-14 pups (Ref. fins) are from prohibited species like the Dusky shark, versus similar allowed species such as the Sandbar shark. In the Pacific Ocean, it occurs off Japan, mainland China and Taiwan, Vietnam, Australia, and New Caledonia in the west, and from southern California to the Gulf of California, around Revillagigedo, and possibly off northern Chile in the east. The upper teeth are broad, triangular, and slightly oblique with strong, coarse serrations, while the lower teeth are narrower and upright, with finer serrations. Large numbers of dusky sharks, mostly juveniles, are caught by sport fishers off South Africa and eastern Australia.