Bull shark

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Bull shark
Temporal range: Miocene–Recent
Carcharhinus leucas, Koh Phangan.jpg
Bull shark from Thailand
Bull shark size.svg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species:
C. leucas
Binomial name
Carcharhinus leucas
Cypron-Range Carcharhinus leucas.svg
Range of bull shark

The bull shark (Carcharhinus leucas), also known as the Zambezi shark (informally zambi) in Africa and Lake Nicaragua shark in Nicaragua, is a species of requiem shark commonly found worldwide in warm, shallow waters along coasts and in rivers. It is known for its aggressive nature, and presence mainly in warm, shallow brackish and freshwater systems including estuaries and (usually) lower reaches of rivers. This aggressive nature is a reason for its population being listed as vulnerable on the IUCN Red List. Shark-culling occurs near beaches to protect beachgoers, which is one of the causes of bull shark populations continuing to decrease. [3]

Contents

Bull sharks are euryhaline and can thrive in both salt and fresh water. They are known to travel far up rivers, and have been known to travel up the Mississippi River as far as Alton, Illinois, [4] about 1,100 kilometres (700 mi) from the ocean, but few freshwater interactions with humans have been recorded. Larger-sized bull sharks are probably responsible for the majority of nearshore shark attacks, including many incidents of shark bites attributed to other species. [5]

Unlike the river sharks of the genus Glyphis , bull sharks are not true freshwater sharks, despite their ability to survive in freshwater habitats.

This shark is the same one that appears in the image of the 2000 colones bill from Costa Rica.

Etymology

The name "bull shark" comes from the shark's stocky shape, broad, flat snout, and aggressive, unpredictable behavior. [6] In India, the bull shark may be confused with the Sundarbans or Ganges shark. In Africa, it is also commonly called the Zambezi River shark, or just "zambi".

Its wide range and diverse habitats result in many other local names, including Ganges River shark, Fitzroy Creek whaler, van Rooyen's shark, Lake Nicaragua shark, [7] river shark, freshwater whaler, estuary whaler, Swan River whaler, [8] cub shark, and shovelnose shark. [9]

Evolution

Some of the bull shark's closest living relatives do not have the capabilities of osmoregulation. Its genus, Carcharhinus , also includes the sandbar shark, which is not capable of osmoregulation. [10]

The bull shark shares numerous similarities with river sharks of the genus Glyphis, and other species in the genus Carcharhinus, but its phylogeny has not been cleared yet. [11]

Anatomy and appearance

Bull sharks are large and stout, with females being larger than males. The bull shark can be up to 81 cm (2 ft 8 in) in length at birth. [12] Adult female bull sharks average 2.4 m (8 ft) long and typically weigh 130 kg (290 lb), whereas the slightly smaller adult male averages 2.25 m (7 ft) and 95 kg (209 lb). While a maximum size of 3.5 m (11 ft) is commonly reported, a single record exists of a female specimen of exactly 4.0 m (13 ft). [5] [13] [14] A 3.25 m (10.7 ft) long pregnant individual reached 450 kg (990 lb). [15] The maximum weight can be over 600 kg (1,300 lb), ranking it among the largest of the requiem sharks. [16] Bull sharks are wider and heavier than other requiem sharks of comparable length, and are grey on top and white below. The second dorsal fin is smaller than the first. The bull shark's caudal fin is longer and lower than that of the larger sharks, and it has a small snout, and lacks an interdorsal ridge. [12]

Bull sharks have a bite force up to 5,914 newtons (1,330 lbf), weight for weight the highest among all investigated cartilaginous fishes. [17]

Exceptional specimens

In early June 2012, off the coast of the Florida Keys near the western part of the Atlantic Ocean, a female believed to measure at least 2.4 m (8 ft) and 360–390 kg (800–850 lb) was caught by members of the R.J. Dunlap Marine Conservation Program. [13] [14] In the Arabian Sea, off the coast of Fujairah in the United Arab Emirates, a pregnant shark weighing 347.8 kg (767 lb) and measuring 3 m (10 ft) long was caught in February 2019, [18] [19] followed by another specimen weighing about 350 kg (770 lb) and measuring about the same in length, in January 2020. [20] [21] Unconfirmed reports suggest that the very largest, exceptional specimens can possibly weigh up to 900 kg (2,000 lb). [22]

Distribution and habitat

The bull shark is commonly found worldwide in coastal areas of warm oceans, in rivers and lakes, and occasionally salt and freshwater streams if they are deep enough. It is found to a depth of 150 m (490 ft), but does not usually swim deeper than 30 m (98 ft). [23] In the Atlantic, it is found from Massachusetts to southern Brazil, and from Morocco to Angola.

Populations of bull sharks are also found in several major rivers, with more than 500 bull sharks thought to be living in the Brisbane River. One was reportedly seen swimming the flooded streets of Brisbane, Queensland, Australia, during the 2010–11 Queensland floods. [24] Several were sighted in one of the main streets of Goodna, Queensland, shortly after the peak of the January 2011, floods. [25] A large bull shark was caught in the canals of Scarborough, just north of Brisbane within Moreton Bay. Still greater numbers are in the canals of the Gold Coast, Queensland. [26] In the warmer months of the year, bull sharks frequent Sydney Harbour. [27] In the Pacific Ocean, it can be found from Baja California to Ecuador.

The bull shark has traveled 4,000 km (2,500 mi) up the Amazon River to Iquitos in Peru [28] and north Bolivia. [2] It also lives in freshwater Lake Nicaragua, in the Ganges and Brahmaputra Rivers of West Bengal, and Assam in Eastern India and adjoining Bangladesh.[ citation needed ] It can live in water with a high salt content as in St. Lucia Estuary in South Africa. Bull sharks have been recorded in the Tigris River since at least 1924 as far upriver as Baghdad, [29] and has been rumored to also inhabit the Cahora Bassa lake upstream of the Zambezi. The species has a distinct preference for warm currents.[ citation needed ]

After Hurricane Katrina, many bull sharks were sighted in Lake Pontchartrain. [30] In July 2023 some local fishermen in the Atchafalaya River have reported increasing numbers. [31] Bull sharks have occasionally gone as far upstream in the Mississippi River as Alton, Illinois. [32] Bull sharks have also been found in the Potomac River in Maryland. [33] [34] A golf course lake at Carbrook, Logan City, Queensland, Australia is the home to several bull sharks. They were trapped following a flood of the Logan and Albert Rivers in 1996. [35] The golf course has capitalized on the novelty and now hosts a monthly tournament called the "Shark Lake Challenge". [36]

Behavior

Freshwater tolerance

The bull shark is the best known of 43 species of elasmobranch, across 10 genera and four families, to have been reported in fresh and/or brackish water. [37] Other species that enter rivers include the stingrays (Dasyatidae, Potamotrygonidae and others) and sawfish (Pristidae). Some skates (Rajidae), smooth dogfishes (Triakidae), and sandbar sharks ( Carcharhinus plumbeus ) regularly enter estuaries.[ citation needed ]

The bull shark is diadromous, meaning they can swim between salt and fresh water with ease, [38] as they are euryhaline fish—able to quickly adapt to a wide range of salinities. Thus, the bull shark is one of the few cartilaginous fishes that have been reported in freshwater systems. Many of the euryhaline fish are bony fishes, such as salmon or tilapia, and are not closely related to bull sharks. Evolutionary assumptions can be made to help explain this sort of evolutionary disconnect, with one being that the bull shark experienced a population bottleneck during the last ice age. [39] This bottleneck may have separated the bull shark from the rest of the Elasmobranchii subclass and favored the genes for an osmoregulatory system.

Elasmobranchs' ability to enter fresh water is limited because their blood is normally at least as salty (in terms of osmotic strength) as seawater through the accumulation of urea and trimethylamine oxide, but bull sharks living in fresh water show a significantly reduced concentration of urea within their blood. [40] Despite this, the solute composition (i.e. osmolarity) of a bull shark in fresh water is still much higher than that of the external environment. This results in a large influx of water across the gills due to osmosis and loss of sodium and chloride from the shark's body. However, bull sharks in fresh water possess several organs with which to maintain appropriate salt and water balance; these are the rectal gland, kidneys, liver, and gills. All elasmobranchs have a rectal gland which functions in the excretion of excess salts accumulated as a consequence of living in seawater. Bull sharks in freshwater environments decrease the salt-excretory activity of the rectal gland, thereby conserving sodium and chloride. [41] The kidneys produce large amounts of dilute urine, but also play an important role in the active reabsorption of solutes into the blood. [41] The gills of bull sharks are likely to be involved in the uptake of sodium and chloride from the surrounding fresh water, [42] whereas urea is produced in the liver as required with changes in environmental salinity. [43] Recent work also shows that the differences in density of fresh water to that of marine waters result in significantly greater negative buoyancies in sharks occupying fresh water, resulting in increasing costs of living in fresh water. Bull sharks caught in freshwater have subsequently been shown to have lower liver densities than sharks living in marine waters. This may reduce the added cost of greater negative buoyancy. [44]

Bull sharks are able to regulate themselves to live in either fresh or salt water. It can live in fresh water for its entire life, but this does not happen, mostly due to the reproductive needs of the shark. Young bull sharks leave the brackish water in which they are born and move out into the sea to breed. While is theoretically possible for bull sharks to live purely in fresh water, experiments conducted on bull sharks found that they died within four years. The stomach was opened and all that was found were two small, unidentifiable fishes. The cause of death could have been starvation since the primary food source for bull sharks resides in salt water. [45]

In a research experiment, the bull sharks were found to be at the mouth of an estuary for the majority of the time. [38] They stayed at the mouth of the river independent of the salinity of the water. The driving factor for a bull shark to be in fresh or salt water, however, is its age; as the bull shark ages, its tolerance for very low or high salinity increases. [38] The majority of the newborn or very young bull sharks were found in the freshwater area, whereas the much older bull sharks were found to be in the saltwater areas, as they had developed a much better tolerance for the salinity. [38] Reproduction is one of the reasons why adult bull sharks travel into the river—it is thought to be a physiological strategy to improve juvenile survival and a way to increase overall fitness of bull sharks. [38] The young are not born with a high tolerance for high salinity, so they are born in fresh water and stay there until they are able to travel out.

Initially, scientists thought the sharks in Lake Nicaragua belonged to an endemic species, the Lake Nicaragua shark (Carcharhinus nicaraguensis). In 1961, following specimen comparisons, taxonomists synonymized them. [46] Bull sharks tagged inside the lake have later been caught in the open ocean (and vice versa), with some taking as few as seven to 11 days to complete the journey. [46]

A study of six bull sharks confined to a stagnant golf course lake in Brisbane, Australia, from 1996 to 2013 uncovered their adaptability to low-salinity environments, marking the longest recorded residency for the species under such conditions, and demonstrating their ability to live indefinitely in low-salinity aquatic environments. [47]

Diet

The bull shark is a marine apex predator, capable of taking a variety of prey. [48] The bull shark's diet consists mainly of bony fish and small sharks, including other bull sharks, [5] and stingrays. Their diet can also include turtles, birds, dolphins, terrestrial mammals, crustaceans, and echinoderms. They hunt in murky waters where it is harder for the prey to see the shark coming. [2] [49] [50] Bull sharks have been known to use the bump-and-bite technique to attack their prey. After the first initial contact, they continue to bite and tackle prey until the prey is unable to flee. [51]

The bull shark is a solitary hunter, though may briefly pair with another bull shark to make hunting and tricking prey easier. [52] [53]

Sharks are opportunistic feeders, [51] and the bull shark is no exception to this, as it is part of the Carcharhinus family of sharks. Normally, sharks eat in short bursts, and when food is scarce, sharks digest for a much longer period of time in order to avoid starvation. [51] As part of their survival mechanism, bull sharks will regurgitate the food in their stomachs in order to escape from a predator. This is a distraction tactic; if the predator moves to eat the regurgitated food the bull shark can use the opportunity to escape. [54]

Reproduction

Bull sharks mate during late summer and early autumn, [10] often in bays and estuaries. [55] After gestating for 12 months, a bull shark may give birth to 1 to 13 live young. [10] [56]

They are viviparous, born live and free-swimming. The young are about 70 cm (27.6 in) at birth. The bull shark does not rear its young; the young bull sharks are born into flat, protected areas. [56] Coastal lagoons, river mouths, and other low-salinity estuaries are common nursery habitats. [5]

The male bull shark is able to begin reproducing around the age of 15 years while the female cannot begin reproducing until the age of 18 years. [56] The size of a fully matured female bull shark to produce viable eggs for fertilization seems to be 175 cm to 235 cm. The courting routine between bull sharks has not been observed in detail as of yet. The male likely bites the female on the tail until she can turn upside down and the male can copulate at that point. Mature females commonly have scratches from the mating process. [57]

Interactions with humans

Bull shark (Bahamas) Bullshark.JPG
Bull shark (Bahamas)

Since bull sharks often dwell in very shallow waters, are found in many types of habitats, are territorial by nature, and have no tolerance for provocation, they may be more dangerous to humans than any other species of shark. [23] Bull sharks are one of the three shark species (along with the tiger shark and great white shark) most likely to bite humans. [6]

One or several bull sharks may have been responsible for the Jersey Shore shark attacks of 1916, which were the inspiration for Peter Benchley's novel Jaws . [58] The speculation that bull sharks may have been responsible is based on two fatal bites occurring in brackish and fresh water.

Bull sharks have attacked swimmers around the Sydney Harbour inlets. [59] [27] In India, bull sharks swim up the Ganges, Bramaputra, Mahanadi, and other Indian rivers and have bitten bathers. Many of these bite incidents were attributed to the Ganges shark, Glyphis gangeticus, a critically endangered river shark species, although the sand tiger shark was also blamed during the 1960s and 1970s.

Bull sharks have also attacked humans off the coast of Florida. [60]

Visual cues

Behavioral studies have confirmed that sharks can take visual cues to discriminate between different objects. The bull shark is able to discriminate between colors of mesh netting that is present underwater. It was found that bull sharks tended to avoid mesh netting of bright colors rather than colors that blended in with the water. Bright yellow mesh netting was found to be easily avoided when it was placed in the path of the bull shark. This was found to be the reason that sharks are attracted to bright yellow survival gear rather than ones that were painted black. [61]

Energy conservation

In 2008, researchers tagged and recorded the movements of young bull sharks in the Caloosahatchee River estuary. They were testing to find out what determined the movement of the young bull sharks. [62] It was found that the young bull sharks synchronously moved downriver when the environmental conditions changed. [62] This large movement of young bull sharks were found to be moving as a response rather than other external factors such as predators. The movement was found to be directly related to the bull shark conserving energy for itself. One way the bull shark is able to conserve energy is that when the tidal flow changes, the bull shark uses the tidal flow in order to conserve energy as it moves downriver. [62] Another way for the bull shark to conserve energy is to decrease the amount of energy needed to osmoregulate the surrounding environment. [62]

Ecology

Humans are the biggest threat to bull sharks. Larger sharks, such as the tiger shark and great white shark, may attack them, but typically only target juveniles. [5] Crocodiles may be a threat to bull sharks in rivers. Saltwater crocodiles have been observed preying on bull sharks in the rivers and estuaries of Northern Australia, [63] and a Nile crocodile was reportedly sighted consuming a bull shark in South Africa. [64]

Conservation

Bull shark in the Aquarium of the Pacific's Shark Lagoon exhibit Bull Shark Aquarium of the Pacific.jpg
Bull shark in the Aquarium of the Pacific's Shark Lagoon exhibit

The bull shark is listed as a vulnerable species on the IUCN Red List and the population is currently reported as decreasing. Despite their status, the species isn't named as a protected species. Threats to the bull shark are numerous, such as getting caught in fishing nets, overfishing for their oil, skin, and meat, pollution to their habitat, and more. [65] In many areas of the world, including Australia and South Africa, there are shark-culling measures around beaches to prevent attacks on beach-goers. Researchers tried to fix the problem of sharks getting too close to land by testing out a device called the SharkSafe Barrier™. This barrier used magnetic and visual stimuli, which utilized rows of piping to create a continuous magnetic field to deter the sharks. However, researchers concluded that the technology needs to be improved upon and tested further before it can be implemented as a reliable safety measure. [3] Other research is being conducted to come up with conservation solutions for the bull sharks. One example is The Nature Conservancy satellite tagging sharks to track their migration and find their habitats in order to guide what areas require further protection projects. [66]

See also

Related Research Articles

<span class="mw-page-title-main">Brackish water</span> Water with salinity between freshwater and seawater

Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater and fresh water together, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root brak. Certain human activities can produce brackish water, in particular civil engineering projects such as dikes and the flooding of coastal marshland to produce brackish water pools for freshwater prawn farming. Brackish water is also the primary waste product of the salinity gradient power process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it is damaging to the environment.

<span class="mw-page-title-main">Lake Nicaragua</span> Largest lake in Central America

Lake Nicaragua or Cocibolca or Granada is a freshwater lake in Nicaragua. Of tectonic origin and with an area of 8,264 km2 (3,191 sq mi), it is the largest lake in Central America, the 19th largest lake in the world and the tenth largest in the Americas, slightly smaller than Lake Titicaca. With an elevation of 32.7 metres (107 ft) above sea level, the lake reaches a depth of 26 metres (85 ft). It is intermittently joined by the Tipitapa River to Lake Managua.

<span class="mw-page-title-main">Fish migration</span> Movement of fishes from one part of a water body to another on a regular basis

Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres. Such migrations are usually done for better feeding or to reproduce, but in other cases the reasons are unclear.

<span class="mw-page-title-main">Freshwater shark</span> Index of animals with the same common name

Freshwater sharks are sharks able to live in freshwater lakes and rivers, including:

<span class="mw-page-title-main">River shark</span> Genus of sharks

Glyphis is a genus in the family Carcharhinidae, commonly known as the river sharks. They live in rivers or coastal regions in and around south-east Asia, Africa and parts of Australia.

<i>Takifugu</i> Genus of fishes

Takifugu, also known by the Japanese name fugu, is a genus of pufferfish with 25 species, most of which are native to salt and brackish waters of the northwest Pacific, but a few species are found in freshwater in Asia or more widely in the Indo-Pacific region. Their diet consists mostly of algae, molluscs, invertebrates and sometimes crustaceans.

<span class="mw-page-title-main">Blacktip reef shark</span> Species of shark

The blacktip reef shark is a species of requiem shark, in the family Carcharhinidae, which can be easily identified by the prominent black tips on its fins. Among the most abundant sharks inhabiting the tropical coral reefs of the Indian and Pacific Oceans, this species prefers shallow, inshore waters. Its exposed first dorsal fin is a common sight in the region. The blacktip reef shark is usually found over reef ledges and sandy flats, though it has also been known to enter brackish and freshwater environments. It typically attains a length of 1.6 m (5.2 ft). Like other sharks, the females are larger than the males.

<span class="mw-page-title-main">Ganges shark</span> Species of shark

The Ganges shark is a critically endangered species of requiem shark found in the Ganges River and the Brahmaputra River of India and Bangladesh. It is often confused with the more common bull shark, which also inhabits the Ganges River and is sometimes incorrectly referred to as the Ganges shark. The genus is currently considered to contain three recent species; genetic evidence has shown that both the Borneo river shark and Irrawaddy river shark should be regarded as synonyms of the Ganges shark, expanding the range of the species to Pakistan, Myanmar, Borneo, and Java. While the other members of the genus Glyphis occur in coastal marine waters as well as rivers, the Ganges shark is found only in fresh water, making it the world's only exclusively freshwater shark. The species remains poorly known and very rare.

<span class="mw-page-title-main">Aquatic ecosystem</span> Ecosystem in a body of water

An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. Freshwater ecosystems may be lentic ; lotic ; and wetlands.

<span class="mw-page-title-main">Dusky shark</span> Species of shark

The dusky shark is a species of requiem shark, in the family Carcharhinidae, occurring in tropical and warm-temperate continental seas worldwide. A generalist apex predator, the dusky shark can be found from the coast to the outer continental shelf and adjacent pelagic waters, and has been recorded from a depth of 400 m (1,300 ft). Populations migrate seasonally towards the poles in the summer and towards the equator in the winter, traveling hundreds to thousands of kilometers. One of the largest members of its genus, the dusky shark reaches more than 4 m (13 ft) in length and 350 kg (770 lb) in weight. 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.

Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the short-finned molly, Poecilia sphenops, which can live in fresh water, brackish water, or salt water.

<span class="mw-page-title-main">Caribbean reef shark</span> Species of shark

The Caribbean reef shark is a species of requiem shark, belonging to the family Carcharhinidae. It is found in the tropical waters of the western Atlantic Ocean from Florida to Brazil, and is the most commonly encountered reef shark in the Caribbean Sea. With a robust, streamlined body typical of the requiem sharks, this species is difficult to tell apart from other large members of its family such as the dusky shark and the silky shark. Distinguishing characteristics include dusky-colored fins without prominent markings, a short free rear tip on the second dorsal fin, and tooth shape and number.

<span class="mw-page-title-main">Daggernose shark</span> Species of shark

The daggernose shark is a little-known species of requiem shark, in the family Carcharhinidae, and the only extant member of its genus. It inhabits shallow tropical waters off northeastern South America, from Trinidad to northern Brazil, favoring muddy habitats such as mangroves, estuaries, and river mouths, though it is intolerant of fresh water. A relatively small shark typically reaching 1.5 m (4.9 ft) in length, the daggernose shark is unmistakable for its elongated, flattened, and pointed snout, tiny eyes, and large paddle-shaped pectoral fins.

<span class="mw-page-title-main">Pigeye shark</span> Species of shark

The pigeye shark or Java shark is an uncommon species of requiem shark, in the family Carcharhinidae, found in the warm coastal waters of the eastern Atlantic and western Indo-Pacific. It prefers shallow, murky environments with soft bottoms, and tends to roam within a fairly localised area. With its bulky grey body, small eyes, and short, blunt snout, the pigeye shark looks almost identical to the better-known bull shark. The two species differ in vertebral count, the relative sizes of the dorsal fins, and other subtle traits. This shark typically reaches lengths of 1.9–2.5 m (6.2–8.2 ft).

<span class="mw-page-title-main">Nervous shark</span> Species of shark

The nervous shark is a species of requiem shark, and part of the family Carcharhinidae, so named because of its timid behavior in regard to humans. It is common in shallow, coastal waters off northern Australia, Papua New Guinea, and the Solomon Islands. A small brownish or grayish shark typically measuring 1.0–1.3 m (3.3–4.3 ft) long, this species has a short, blunt snout, oval eyes, and a relatively large second dorsal fin. The leading margins of most fins are finely edged with black, and the lower caudal fin lobe is black-tipped.

<span class="mw-page-title-main">Australian blacktip shark</span> Species of shark

The Australian blacktip shark is a species of requiem shark, in the family Carcharhinidae, endemic to northern and eastern Australia. Favoring the upper and middle parts of the water column, it can be found from the intertidal zone to a depth of 50 m (160 ft). Appearance-wise this species is virtually identical to the common blacktip shark, from which it can be reliably distinguished only by its lower vertebra number and by genetic markers. Generally reaching 1.5–1.8 m (4.9–5.9 ft) in length, it is a fairly stout-bodied, bronze-colored shark with a long snout and black-tipped fins.

<span class="mw-page-title-main">Milk shark</span> Species of shark

The milk shark is a species of requiem shark, and part of the family Carcharhinidae, whose common name comes from an Indian belief that consumption of its meat promotes lactation. The largest and most widely distributed member of its genus, the milk shark typically measures 1.1 m (3.6 ft) long, and can be found in coastal tropical waters throughout the eastern Atlantic and the Indo-Pacific regions. Occurring from the surface to a depth of 200 m (660 ft), this species is common near beaches and in estuaries, and has been recorded swimming up rivers in Cambodia. Juveniles are known to inhabit tidal pools and seagrass meadows. The milk shark has a slender body with a long, pointed snout and large eyes, and is a nondescript gray above and white below. This shark can be distinguished from similar species in its range by the long furrows at the corners of its mouth, and seven to 15 enlarged pores just above them.

The narrow sawfish, also known as the pointed sawfish or knifetooth sawfish, is a species of sawfish in the family Pristidae, part of the Batoidea, a superorder of cartilaginous fish that include the rays and skates. Sawfish display a circumglobal distribution in warm marine and freshwater habitats. Their extant biodiversity is limited to five species belonging to two genera. The sawfishes are characterised by the long, narrow, flattened rostrum or extension on their snout. This is lined with sharp transverse teeth, arranged in a way that resembles the teeth of a saw and are used for killing prey. It is found in the shallow coastal waters and estuaries of the Indo-West Pacific, ranging from the Persian Gulf to southern Japan, Papua New Guinea and northern Australia. It is the only living member of the genus Anoxypristis, but was previously included in the genus Pristis. Compared to Pristis, Anoxypristis has a narrower rostral saw with numerous teeth on the distal part and no teeth on the basal one-quarter. It reaches a length of up to 3.5 m (11 ft).

<span class="mw-page-title-main">Atlantic stingray</span> Species of cartilaginous fish

The Atlantic stingray is a species of stingray in the family Dasyatidae, common along the Atlantic coast of North America from Chesapeake Bay to Mexico, including brackish and freshwater habitats. It may be distinguished from other stingrays in the area by its relatively elongated snout. This species is of little commercial importance, other than for sale in the aquarium industry.

<span class="mw-page-title-main">White-edge freshwater whipray</span> Species of cartilaginous fish

The white-edge freshwater whipray is an extremely rare species of stingray in the family Dasyatidae, native to four river systems in Southeast Asia. Measuring up to 60 cm (24 in) across, this ray has an oval pectoral fin disc and a very long, whip-like tail without fin folds. It can be identified by the presence of a sharply delineated white band running around the margin of its otherwise brown disc, as well as by its white tail and a band of dermal denticles along the middle of its back. This species feeds on benthic invertebrates and is aplacental viviparous. Its two long tail spines are potentially dangerous to humans. The International Union for Conservation of Nature (IUCN) has assessed the white-edge freshwater whipray as Endangered, as it is under heavy pressure from fishing and habitat loss, degradation, and fragmentation.

References

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  3. 1 2 O'Connell, Craig Patrick; Gressle, Juliet; Crews, Julia; King, Andre A.; He, Pingguo (2022-01). "Evaluating the effects of a SharkSafe Barrier™ shoreline deployment on bull shark ( Carcharhinus leucas ) behaviour". Aquatic Conservation: Marine and Freshwater Ecosystems. 32 (1): 55–65. doi:10.1002/aqc.3732. ISSN 1052-7613
  4. ↑ Sharks In Illinois. In-Fisherman (16 July 2012). Retrieved on 30 November 2013.
  5. 1 2 3 4 5 "Bull shark". Florida Museum of Natural History. Retrieved 8 September 2006.
  6. 1 2 "Bull shark". National Geographic. Archived from the original on 4 July 2007. Retrieved 3 April 2011.
  7. ↑ "Biology of Sharks and Rays". ReefQuest Centre for Shark Research. Retrieved 19 August 2010.
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