Sharks Codexery

Northern river shark

A rare requiem shark of turbid tidal rivers and coastal waters.

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Northern river shark

CSIRO National Fish Collection · via Wikipedia: Northern river shark · CC BY 3.0

The northern river shark is a rare requiem shark that patrols the murky rivers and coastal waters of northern Australia and Papua New Guinea.[1] It is one of the most threatened sharks on the planet, with perhaps no more than 250 mature individuals left in the wild.[2]

Scientific classification

  1. KingdomAnimalia
  2. PhylumChordata
  3. ClassChondrichthyes
  4. SubclassElasmobranchii
  5. DivisionSelachii
  6. OrderCarcharhiniformes
  7. FamilyCarcharhinidae
  8. GenusGlyphis
  9. SpeciesGlyphis garricki

Named by Compagno, W. T. White & Last, 2008

Close relatives

Other species of Glyphis with a Codexery entry.

Sources: Wikipedia taxobox: Northern river shark (CC BY-SA 4.0) · order, family and genus agree with WoRMS AphiaID 398263 (CC BY 4.0)

Conservation status

Vulnerable (VU)

  1. LC
  2. NT
  3. VU▲ this species
  4. EN
  5. CR
  6. EW
  7. EX
Population trend
Not held in our sources — see the assessment
Assessment published
2021

Source: IUCN Red List assessment · GBIF copy of the Red List category

How big is it?

Size comparison: Northern river shark and a personA 2.5 m long northern river shark drawn to scale next to a 1.8 m tall person. Schematic shapes, not a likeness.2.5 m1.8 m

Largest length in the source, 2.5 m, next to a 1.8 m person.

Diagram: drawn by Codexery, schematic shapes to scale (not a likeness). Length: Wikipedia: Northern river shark

Where the northern river shark has been recorded

Where the northern river shark has been recorded3 mapped locations from 1,963 GBIF occurrence records; marked places: Northern Territory, King Sound, Ord River, Adelaide River, Alligator Rivers, DaruNorthern TerritoryKing SoundOrd RiverAdelaide RiverAlligator RiversDaru

Each dot is a place where the species has been observed and reported (1,963 records, half-degree grid) — not a modelled range. 16 inland records left out (institution coordinates).

Map: drawn by Codexery. Data: GBIF occurrence search (records CC0 / CC BY) · Natural Earth basemap (public domain) · place coordinates: Wikipedia (CC BY-SA 4.0)

Description

Its snout is broadly rounded, and its tiny eyes have nictitating membranes, which are clear eyelids that protect the eye.[3] The skin is covered in small, oval, overlapping scales called dermal denticles, each with three horizontal ridges.[3] This shark has a chunky body and a broad, flat head, just like its close relatives.[3] A triangular flap of skin splits each nostril into one big opening and one tiny one.[3]

The upper teeth stand upright, are triangle-shaped, and have serrated edges; the lower teeth are skinnier and go straight or curve just a little.[3] Pelvic fins are triangle-shaped and have rear edges that are almost straight.[3] On top, this shark is steel-gray, and underneath it's white; the line between those colors is sharp and sits well below the eye.[3] The biggest one ever recorded measured 2.5 meters long.[3]

You can tell this species apart from the speartooth shark by its fewer vertebrae (137 to 151, not 213 to 222) and a lower, jagged gray-white color line.[3]

Biology and ecology

The northern river shark seems built for hunting fish in murky water, with slender teeth, small eyes, and lots of ampullae of Lorenzini—sensory organs that pick up electrical fields.[4] Young are born at under 67 centimeters long.[5] Like all requiem sharks, the northern river shark gives birth to live young; the babies first use up their yolk sac and then form a placental connection to their mom.[4] One female that scientists looked at was carrying nine babies.[5]

Males become mature when they're between 1.2 and 1.4 meters long, and females mature between 1.4 and 1.7 meters.[5]

Distribution and habitat

People have spotted the northern river shark in King Sound, the Ord River, and Doctors Creek near Derby in Western Australia; the Adelaide and Alligator Rivers in the Northern Territory; and around Daru and possibly the Fly River in Papua New Guinea.[1]

Human interactions

This shark seems very rare, though there might be more groups of them out there in Australia and Papua New Guinea that we haven't found yet.[2] In Papua New Guinea, there are no rules that stop people from catching this shark.[6] Habitat degradation may pose a further threat.[2]

Taxonomy and phylogeny

The very first northern river sharks ever found were two newborn males from Papua New Guinea, discovered by New Zealand fish expert Jack Garrick—and that's who the species is named after.[3]

References

  1. Wikipedia, "Northern river shark" (CC BY-SA 4.0), which cites: Compagno, L.J.V., "Descriptions of new Australian Chondrichthyans", CSIRO Marine and Atmospheric Research, 2008, p. 203–226}} (ISBN corrected) {{Listed Invalid ISBN; Pillans, R.D., "Observations on the distribution, biology, short-term movements and habitat requirements of river sharks Glyphis spp. in northern Australia", Endangered Species Research, 25 August 2009, p. 321–332; White, W.T., "Rediscovery of the Threatened River Sharks, Glyphis garricki and G. glyphis, in Papua New Guinea", PLOS ONE, 7 October 2015 (we also rea en.wikipedia.org
  2. Wikipedia, "Northern river shark" (CC BY-SA 4.0), which cites: Kyne, P.M., "Glyphis garricki", 2021 (we also read that source) en.wikipedia.org
  3. Wikipedia, "Northern river shark" (CC BY-SA 4.0), which cites: Compagno, L.J.V., "Descriptions of new Australian Chondrichthyans", CSIRO Marine and Atmospheric Research, 2008, p. 203–226}} (ISBN corrected) {{Listed Invalid ISBN (original not read by us) en.wikipedia.org
  4. Wikipedia, "Northern river shark" (CC BY-SA 4.0), which cites: Kyne, P.M., "Glyphis garricki", 2021; Thorburn, D.C., D.L. Morgan, A.J. Rowland and H.S. Gill. (February 2004). The northern river shark (Glyphis sp. C) in Western Australia . Report to the National (we also read that source) en.wikipedia.org
  5. Wikipedia, "Northern river shark" (CC BY-SA 4.0), which cites: Pillans, R.D., "Observations on the distribution, biology, short-term movements and habitat requirements of river sharks Glyphis spp. in northern Australia", Endangered Species Research, 25 August 2009, p. 321–332; Compagno, L.J.V., "Descriptions of new Australian Chondrichthyans", CSIRO Marine and Atmospheric Research, 2008, p. 203–226}} (ISBN corrected) {{Listed Invalid ISBN (we also read that source) en.wikipedia.org
  6. Wikipedia, "Northern river shark" (CC BY-SA 4.0), which cites: Kyne, P.M., "Glyphis garricki", 2021; White, W.T., "Rediscovery of the Threatened River Sharks, Glyphis garricki and G. glyphis, in Papua New Guinea", PLOS ONE, 7 October 2015 (we also read that source) en.wikipedia.org

Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Northern river shark (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.

Related entries

Same family (Carcharhinidae)

Atlantic sharpnose shark Rhizoprionodon terraenovaeAustralian blackspot shark Carcharhinus coatesi

Named in this entry

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Test yourself

Three questions drawn from this entry’s sources. Pick an answer to check it.

1. To which genus does the northern river shark belong?

Correct.

Not quite. The answer is Glyphis.

From the source: “The northern river shark or New Guinea river shark (Glyphis garricki) 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.”

2. What is the IUCN Red List category of the northern river shark?

Correct.

Not quite. The answer is Vulnerable.

From the source: “Very rare and facing threats from commercial and recreational fishing, and perhaps also habitat degradation, this species has been assessed as Vulnerable by the International Union for Conservation of Nature.”

3. Who first scientifically described the northern river shark?

Correct.

Not quite. The answer is Leonard Compagno.

From the source: “C" until 2008, when it was formally described by Leonard Compagno, William White, and Peter R.”

Answers checked against the source article

Sources

Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.

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