Speartooth shark

Last updated

Speartooth shark
Speartooth shark melbourne.jpg
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: Glyphis
Species:
G. glyphis
Binomial name
Glyphis glyphis
Glyphis glyphis rangemap.png
Range of the speartooth shark

The speartooth shark (Glyphis glyphis) is a rare species of river shark, belonging to the family Carcharhinidae. It inhabits coastal marine waters and tidal reaches of large tropical rivers in northern Australia and New Guinea. Despite being a member of the river shark genus, it is also found in near-shore marine waters, favoring highly turbid environments over a wide range of salinities. This robustly built, gray-colored shark is characterized by a short and broad snout, tiny eyes, a relatively large second dorsal fin, and a black blotch beneath each pectoral fin near the tip. Another identifying trait is its teeth, which are large, triangular, and serrated in the upper jaw and narrow, spear-like, and serrated only near the tips in the lower jaw. Adults grow to about 2.6 m (8.5 ft) long.

Contents

Preying on demersal bony fishes and crustaceans, the speartooth shark is adapted for hunting in near-complete darkness. It is not as active as other requiem sharks, moving upstream and downstream with tidal currents so as to save energy. Reproduction is viviparous, with females forming a placental connection to their young, though details are unknown. The speartooth shark is threatened by incidental capture in commercial and recreational fisheries, as well as by habitat degradation. Given its small population, restricted range, and stringent habitat requirements, this species is highly susceptible to these pressures and has been listed as vulnerable by the International Union for Conservation of Nature.

Taxonomy

Muller and Henle's original illustration of Carcharias (Prionodon) glyphis Carcharias glyphis by muller and henle.png
Müller and Henle's original illustration of Carcharias (Prionodon) glyphis

German biologists Johannes Müller and Jakob Henle originally described the speartooth shark as Carcharias (Prionodon) glyphis, in their 1839–41 Systematische Beschreibung der Plagiostomen. They based their account on a stuffed juvenile female 1 m (3.3 ft) long, of unknown origin (possibly the Indian Ocean or the South China Sea). [2] [3] In 1843, Swiss-American zoologist Louis Agassiz proposed the new genus Glyphis for this species and a fossil relative from Britain, G. hastalis . However, the use of Glyphis to encompass the river sharks did not gain wide acceptance until Jack Garrick's 1982 revision of Carcharhinus . [4]

Müller and Henle's type specimen remained the sole known record of the speartooth shark until specimens of the "Bizant river shark" (Glyphis sp. A) were caught in Australia in 1982. Subsequently, work by Leonard Compagno, William White, and Peter Last confirmed initial suspicions that "sp. A" was the same species as G. glyphis. [5] Thus, in Australia, this shark may also be referred to as the Bizant river shark or the Queensland river shark. [6]

Distribution and habitat

Juvenile and subadult speartooth sharks are found in a few large, mangrove-lined tropical rivers in northern Australia and New Guinea, from the estuary to hundreds of kilometers upstream; a single possible record from the South China Sea exists. [3] [7] In Queensland, it occurs in the Wenlock, Ducie, and Bizant Rivers, and perhaps also the Normanby, Hey, and Embly Rivers. In the Northern Territory, it is known from the Adelaide River and the Alligator Rivers. The river sharks in the Ord River of Western Australia may also be of this species. [6] [8] In New Guinea, this species has been reported from Daru island, near Port Romilly and in the Fly River. [9] [10]

Newborn to subadult speartooth sharks exclusively inhabit areas with fast tidal currents and muddy bottoms; the flowing water produces heavy turbidity, such as that <1% of sunlight penetrates beyond a depth of 1 m (3.3 ft). The salinity level of these waters range from nearly fresh (0.8 ppt) to nearly marine (28 ppt), and temperatures range from 25 to 33 °C (77 to 91 °F). Younger sharks are generally found further upstream than older ones. A study that tracked three individuals in the Adelaide River reported that they moved upstream with the flooding tide and downstream with the ebbing tide, averaging 10–12 km (6.2–7.5 mi) each way. The average swimming depth was determined for one individual to be 7.7 m (25 ft), in the middle of the water column. [11] Adults were entirely unknown until 2014, when three specimens (two males and one female) were documented by scientists visiting fishing villages on Daru island, Papua New Guinea. All three were caught in coastal waters off the island. [10] No evidence exists of segregation by sex. [8]

Recently in 2024 a new population where found in the Roper River of the Northern Territory, the first time ever documented living in that area, there was enough living specimens for a viable population and keeping the species alive.

Description

Without any known adult specimens, the maximum size of this species has historically been labelled with considerable uncertainty. In 2014, the first known adults were documented and on this basis it reaches a length around 2.6 m (8.5 ft). [10] The speartooth shark has a streamlined, rather robust body with a short, wide head. The snout is flattened, with large nostrils divided into incurrent and excurrent openings by large, triangular flaps of skin. The eyes are small and equipped with nictitating membranes (protective third eyelids). The sizable, arched mouth has very short furrows at the corners. It has 26–29 upper and 27–29 lower tooth rows. The teeth are tall and upright; those in the upper jaw are wide and triangular with serrated edges, while those in the lower jaw are narrow and spear-like with serrations only near the tip, and tiny cusplets at the base in very young individuals. There are five pairs of gill slits, with the first pair longer than the others. [5] [9]

The large pectoral fins have strongly convex leading and concave trailing margins, and blunt tips. The pelvic fins are triangular with nearly straight margins. The first dorsal fin originates over the pectoral fin insertions, and is broadly triangular with a narrow apex and a concave trailing margin. The second dorsal fin measures about 67–77% as tall as the first and is similar in shape; there is no midline ridge between the dorsal fins. The anal fin is almost as large as the second dorsal fin and lies slightly behind; it has a deep notch in the posterior margin. The caudal fin is asymmetrical; the lower lobe is narrow and well-developed, while the upper lobe has a gently convex upper margin and a prominent notch in the ventral margin near the tip. The body is covered by small, overlapping oval-shaped dermal denticles bearing three or five horizontal ridges leading to marginal teeth. This species is plain slate-gray above, including the upper surfaces of the pectoral and pelvic fins, and the caudal fin; the underside is white. The boundary between dark and light runs through the bottom rim of the eye, through the gill slits, over the flank well above the pelvic fins, and onto the upper caudal fin lobe. The fins darken towards the posterior margins, forming a black edge on the upper caudal fin lobe; each pectoral fin also has a black blotch underneath, near the tip. The eyes are ringed in white. [5] [9]

Biology and ecology

The speartooth shark seems to be relatively sluggish in nature, moving with the tides so as to conserve energy. Its activity levels are unaffected by day or night, reflecting the constant darkness of its environment. [11] Small eyes and abundant ampullae of Lorenzini suggest that this shark relies more on electroreception than sight to hunt, while the large second dorsal fin enhances its ability to maneuver at slow speeds in fast currents. It has slender teeth adept for catching bony fishes and crustaceans, mostly on or near the bottom. Known prey of juveniles include Macrobrachium prawns, Taenoides or Trypauchen burrowing gobies, ariid catfish, the threadfin Polydactylus macrochir , the gudgeon Prionobutis microps , the benthic croaker Nibea squamosa and the bream Nematalosa erebi . [7] [11] Very little is known about the feeding habits of adults, but many bony fish spines and a stingray spine were found embedded in the jaws of the only documented adult female. [10] As in other requiem sharks, the speartooth shark is viviparous: when the developing embryo exhausts its supply of yolk, the yolk sac develops into a placental connection through which the mother delivers nourishment. Birthing seems to occur from October to December, near the end of the dry season, with newborns measuring around 50–59 cm (20–23 in) long. [9] [11] Upon being captured a female gave birth to a single fully developed pup, about 65 cm (2.13 ft) long, and anecdotal information indicates a litter size of six to seven. [10] The growth rate of young sharks is probably around 19 cm (7.5 in) per year. [8]

Human interactions

The speartooth shark is not known to pose a danger to humans. [12] Extremely rare like other river sharks, its global population has been estimated to number no more than 2,500 mature individuals, with no more than 250 in any subpopulation. [1] This species is caught incidentally by commercial fisheries using gillnets and longlines, such as the barramundi (Lates calcarifer) gillnet fishery in Queensland (barramundi fisheries in New South Wales have been prohibited from rivers occupied by this species since 2005). Significant numbers are also taken by recreational anglers and bow fishers. Captured sharks might be eaten, used to bait crab pots, or discarded on land. Habitat degradation represents a third threat to the speartooth shark: the Fly River in Papua New Guinea has been severely affected by pollutants from mining activities, while proposed mining and dredging projects in the Port Musgrave area and uranium mining in Kakadu National Park are also of concern. [1] [6] [8]

The range of conservation threats faced by the speartooth shark, coupled with its small population and restricted range and habitat preferences, have led the International Union for Conservation of Nature to assess it as vulnerable. [1] Furthermore, in Australia, it has been listed as critically endangered on the 1999 Commonwealth Environment Protection and Biodiversity Conservation Act. The speartooth shark is within the scope of the Sawfish and river shark multispecies recovery plan made under the EPBC Act. [13] It has also been listed as vulnerable on the 2000 Territory Parks and Wildlife Conservation Act, though a management plan has yet to be enacted. Sharks in the Kakadu and Rinyirru National Parks are protected somewhat from habitat alteration, if not fishing. [6] [8] No regulations restrict the capture of this species in Papua New Guinea. [10]

Related Research Articles

<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.

<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">Prickly dogfish</span> Species of fish

The prickly dogfish is a poorly known species of dogfish shark in the family Oxynotidae, inhabiting temperate Australian and New Zealand waters. Reaching a length of 75 cm (30 in), this brown to gray shark has a very thick body with a prominent "humpback" and extremely rough skin. It is further characterized by two enormous, sail-like dorsal fins placed relatively close together. Both dorsal fins have a spine embedded mostly within the fleshy leading portion of the fin; the first dorsal spine is tilted forward.

<span class="mw-page-title-main">Slender smooth-hound</span> Species of shark

The slender smooth-hound or gollumshark is a species of ground shark in the family Pseudotriakidae. It is endemic to the waters around New Zealand, where it is usually found close to the bottom over the continental slope at depths of 300–600 m (980–1,970 ft). An extremely slim, plain brownish shark reaching 1.1 m (3.6 ft) in length, the slender smooth-hound can be identified by its broad, flattened head with a long, distinctively bell-shaped snout. Its mouth is angular with short furrows at the corners, and contains a very high number of tooth rows in both jaws. Its two dorsal fins are roughly equal in size.

<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">Bignose shark</span> Species of shark

The bignose shark is a species of requiem shark, in the family Carcharhinidae. Distributed worldwide in tropical and subtropical waters, this migratory shark frequents deep waters around the edges of the continental shelf. It is typically found at depths of 90–430 m (300–1,410 ft), though at night it may move towards the surface or into shallower water. The bignose shark is plain-colored and grows to at least 2.7–2.8 m (8.9–9.2 ft) in length. It has a long, broad snout with prominent nasal skin flaps, and tall, triangular upper teeth. Its pectoral fins are long and almost straight, and there is a ridge on its back between the two dorsal fins.

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

The graceful shark or Queensland shark is a species of requiem shark, in the family Carcharhinidae, found in the tropical Indo-Pacific, from the Gulf of Aden to northern Australia. It is a midwater species that has been recorded to a depth of 50 m (160 ft). A stoutly built shark growing up to 1.7 m (5.6 ft) long, the graceful shark has a short, wedge-shaped snout, large, sickle-shaped pectoral fins and first dorsal fin, and black tips on most fins.

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

The hardnose shark is a species of requiem shark, in the family Carcharhinidae, so named because of the heavily calcified cartilages in its snout. A small bronze-coloured shark reaching a length of 1.1 m (3.6 ft), it has a slender body and a long, pointed snout. Its two modestly sized dorsal fins have distinctively elongated rear tips. The hardnose shark is widely distributed in the western Indo-Pacific, from Kenya to southern China and northern Australia. It inhabits warm, shallow waters close to shore.

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

The creek whaler is a common species of requiem shark, and part of the family Carcharhinidae, endemic to northern Australia. It frequents shallow waters close to shore, including estuaries. This small, stocky shark usually grows to 1.0–1.3 m (3.3–4.3 ft) long and is brownish in color without conspicuous fin markings. It can be identified by its long snout, large, triangular pectoral fins, and large, anteriorly positioned first dorsal fin.

<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">Pondicherry shark</span> Species of shark

The Pondicherry shark is an extremely rare species of requiem shark, in the family Carcharhinidae. A small and stocky gray shark, it grows not much longer than 1 m (3.3 ft) and has a fairly long, pointed snout. This species can be identified by the shape of its upper teeth, which are strongly serrated near the base and smooth-edged near the tip, and by its first dorsal fin, which is large with a long free rear tip. Furthermore, this shark has prominent black tips on its pectoral fins, second dorsal fin, and caudal fin lower lobe.

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

The smoothtooth blacktip shark is a species of requiem shark in the family Carcharhinidae. It is known only from the type specimen caught from the Gulf of Aden, off eastern Yemen, and a handful of additional specimens caught from the Persian Gulf, off Kuwait. Reaching 1.3 m (4.3 ft) in length, this species has a stocky greenish-colored body, a short snout, and black-tipped fins. It can be distinguished from similar species by its teeth, which are narrow, erect, and smooth-edged.

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

The blackspot shark is a small species of requiem shark in the family Carcharhinidae found in the tropical Indo-West Pacific Ocean between latitudes 24°N and 30°S, from the surface to a depth around 40 m (130 ft). Its length is a little under one meter (yard) and it is not considered to be dangerous to humans. It feeds mainly on fish, crustaceans, and squid. This shark is also caught in small-scale fisheries for human consumption.

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

The spot-tail shark, or sorrah shark, is a species of requiem shark, in the family Carcharhinidae, found in the tropical Indo-West Pacific Ocean between latitudes 31°N and 31°S from the surface to a depth around 72 m (236 ft). This shark grows to about 1.6 m. It is fished commercially over much of its range and the IUCN considers it to be near threatened.

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

The Australian weasel shark is an uncommon species of ground shark in the family Hemigaleidae. It inhabits shallow waters off northern Australia to a depth of 170 m (560 ft); smaller sharks frequent sand and seagrass habitat and shift to coral reefs as they grow older. A slim, drab species reaching a length of 1.1 m (3.6 ft), it has sickle-shaped fins with dark tips on the second dorsal fin and caudal fin upper lobe. Its upper teeth are broad with strong serrations only on the trailing edge. The lateral line along each side is prominent and exhibits a downward curve below the second dorsal fin.

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

The smalleye pygmy shark is a little-known species of squaliform shark in the family Dalatiidae, found in water 150–2,000 m (490–6,560 ft) deep near Japan, the Philippines, and Australia. It migrates vertically daily, spending the day in deep water and the night in shallower water. One of the smallest shark species, the smalleye pygmy shark is known to reach only 22 cm (8.7 in) long. It has a blackish, spindle-shaped body with relatively small eyes, and a spine preceding the first dorsal fin, but not the second. Bioluminescent photophores occur on its underside, which may serve to disguise its silhouette from predators. This species feeds on small squid, krill, shrimp, and bony fishes. It is aplacental viviparous. The International Union for Conservation of Nature has assessed it as Least Concern, citing its wide distribution and lack of threat from fisheries.

<span class="mw-page-title-main">Slender sawtail catshark</span> Species of shark

The slender sawtail catshark is a little-known species of catshark, part of the family Scyliorhinidae, endemic to northern Australia. It is found over the continental slope in 290–470 m (950–1,540 ft) on water. Growing to 34 cm (13 in) long, this shark has a slim gray body with four dark saddle markings below the dorsal fins and on the caudal fin, as well as a prominent crest of enlarged dermal denticles along the dorsal edge of the caudal fin. The slender sawtail catshark is not valued by fisheries but is taken as bycatch. The International Union for Conservation of Nature (IUCN) presently lacks enough information to assess its conservation status.

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

The northern river shark or New Guinea river shark is a species of requiem shark, in the family Carcharhinidae, found in scattered tidal rivers and associated coastal waters in northern Australia and in Papua New Guinea. This species inhabits areas with poor visibility, soft bottoms, and large tides, with immature sharks ranging into fresh and brackish water. It is similar to other river sharks in having a stocky grey body with a high back, tiny eyes, and broad fins. It measures up to 2.5 m (8.2 ft) long.

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

The Australian blackspot shark or Coates's shark is a species of requiem shark found off northern Australia and possibly also off the coast of New Guinea. It belongs to a species complex of Blackspot sharks in the family Carcharhinidae. These sharks are not widely studied due to their cryptic nature, but there was a recent reclassification distinguishing it from the Whitecheek shark and the Blackspot Shark in 2012. Much of the existing literature predates this reclassification and groups the Australian blackspot shark with the aforementioned closely related species.

References

  1. 1 2 3 4 Kyne, P.M.; Rigby, C.L.; Darwall, W.R.T.; Grant, I.; Simpfendorfer, C. (2021). "Glyphis glyphis". IUCN Red List of Threatened Species . 2021: e.T39379A68624306. doi: 10.2305/IUCN.UK.2021-2.RLTS.T39379A68624306.en . Retrieved 19 November 2021.
  2. ↑ Müller, J. & F.G.J. Henle (1838–41). Systematische Beschreibung der Plagiostomen. Veit und Comp. p. 40.
  3. 1 2 Roberts, T. R. (21 May 2007). "A new record for the speartooth carcharhinid shark Glyphis glyphis from Pulo Condor, South China Sea". Natural History Bulletin of the Siam Society. 54 (2): 279–283.
  4. ↑ Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Food and Agricultural Organization. pp. 506–509. ISBN   92-5-101384-5.
  5. 1 2 3 Compagno, L.J.V.; W.T. White & P.R. Last (2008). "Glyphis garricki sp. nov., a new species of river shark (Carcharhiniformes: Carcharhinidae) from northern Australia and Papua New Guinea, with a redescription of Glyphis glyphis (Müller & Henle, 1839)". In Last, P.R.; W.T. White & J.J. Pogonoski (eds.). Descriptions of new Australian Chondrichthyans. CSIRO Marine and Atmospheric Research. pp. 203–226. ISBN   978-0-1921424-1-2. (ISBN corrected) ISBN   1-921424-18-2 (invalid, listed in publication).
  6. 1 2 3 4 Department of the Environment, Water, Heritage and the Arts (2010). Glyphis glyphis– Speartooth Shark. Species Profile and Threats Database, Department of the Environment, Water, Heritage and the Arts, Canberra. Retrieved on 13 September 2010.
  7. 1 2 Peverell, S.C.; G.R. McPherson; R.N. Garrett & N.A. Gribble (2006). "New records of the River Shark Glyphis (Carcharhinidae) reported from Cape York Peninsula, northern Australia". Zootaxa. 1233: 53–68. doi:10.11646/zootaxa.1233.1.2.
  8. 1 2 3 4 5 Stevens, J.D., R.D. Pillans and J. Salini (2005). Conservation Assessment of Glyphis sp. A (Speartooth Shark), Glyphis sp. C (Northern River Shark), Pristis microdon (Freshwater Sawfish) and Pristis zijsron (Green Sawfish). CSIRO Marine Research, Hobart, Tasmania. Retrieved on 13 September 2010.
  9. 1 2 3 4 Last, P.R. & J.D. Stevens (2009). Sharks and Rays of Australia (second ed.). Harvard University Press. p. 276–277. ISBN   978-0-674-03411-2.
  10. 1 2 3 4 5 6 White, W.T.; S.A. Appleyard; B. Sabub; P.M. Kyne; M. Harris; R. Lis; L. Baje; T. Usu; J.J. Smart; S. Corrigan; L. Yang & G.J.P. Naylor (7 October 2015). "Rediscovery of the Threatened River Sharks, Glyphis garricki and G. glyphis, in Papua New Guinea". PLOS ONE. 10 (published online): e0140075. Bibcode:2015PLoSO..1040075W. doi: 10.1371/journal.pone.0140075 . PMC   4596488 . PMID   26445387.
  11. 1 2 3 4 Pillans, R.D.; J.D. Stevens; P.M. Kyne & J. Salini (25 August 2009). "Observations on the distribution, biology, short-term movements and habitat requirements of river sharks Glyphis spp. in northern Australia" (PDF). Endangered Species Research. 10 (published online): 321–332. doi: 10.3354/esr00206 .
  12. ↑ Froese, Rainer; Pauly, Daniel (eds.) (2010). "Glyphis glyphis" in FishBase. September 2010 version.
  13. ↑ Department of the Environment (2015). Sawfish and river shark multispecies recovery plan. Department of the Environment, Canberra.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.