The northern river shark or New Guinea river shark (''Glyphis garricki'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

requiem shark Requiem sharks are sharks of the family Carcharhinidae in the order Carcharhiniformes. They are migratory, live-bearing sharks of warm seas (sometimes of brackish or fresh water) and include such species as the tiger shark, bull shark, le ...

, in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Carcharhinidae, found in scattered

tidal river A tidal river is a river whose flow and level are influenced by tides. A section of a larger river affected by the tides is a tidal reach, but it may sometimes be considered a tidal river if it has been given a separate name. Generally, tidal ri ...

s and associated coastal waters in northern

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

and in

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

. This species inhabits areas with poor visibility, soft bottoms, and large

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravity, gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide t ...

s, with immature sharks ranging into

fresh Fresh or FRESH may refer to: People *DJ Fresh (born 1977), UK-based drum and bass artist *DJ Fresh (producer), US-based R&B producer born Marqus Brown Arts, entertainment, and media Films * ''Fresh'' (1994 film), a crime film * ''Fresh'' (200 ...

and

brackish water 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 (salt water) and fresh water together, as in estua ...

. 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 long. Northern river sharks are likely

piscivorous A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evoluti ...

. This species is

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

, with females bearing litters of 9 young possibly every other year before the

wet season The wet season (sometimes called the Rainy season) is the time of year when most of a region's average annual rainfall occurs. It is the time of year where the majority of a country's or region's annual precipitation occurs. Generally, the sea ...

. Very rare and facing threats from

commercial Commercial may refer to: * a dose of advertising conveyed through media (such as - for example - radio or television) ** Radio advertisement ** Television advertisement * (adjective for:) commerce, a system of voluntary exchange of products and s ...

and

recreational fishing Recreational fishing, also called sport fishing or game fishing, is fishing for leisure, exercise or competition. It can be contrasted with commercial fishing, which is professional fishing for profit; or subsistence fishing, which is fishing ...

, and perhaps also

habitat degradation Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

, this species has been assessed as Vulnerable by the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

Taxonomy

The first known specimens of the northern river shark, two newborn males from Papua New Guinea, were discovered by

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish ( Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of Octobe ...

Jack Garrick John Andrew Frank "Jack" Garrick (1928 – August 30, 2018) was a New Zealand ichthyologist. He specialized in elasmobranchs and published many books and articles about shark and ray biology. In 1982, he published a thorough taxonomy on sharks of ...

, after whom the species was eventually named. This shark was referred to as "''Glyphis'' sp. C" until 2008, when it was formally described by

Leonard Compagno Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organi ...

, William White, and Peter R. Last in a

Commonwealth Scientific and Industrial Research Organisation The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government agency responsible for scientific research. CSIRO works with leading organisations around the world. From its headquarters in Canberra, CSIRO ...

paper. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

is a female long, collected from the

East Alligator River Alligator Rivers is the name of an area in an Arnhem Land region of the Northern Territory of Australia, containing three rivers, the East, West, and South Alligator Rivers. It is regarded as one of the richest biological regions in Australia ...

Kakadu National Park Kakadu National Park is a protected area in the Northern Territory of Australia, southeast of Darwin. It is a World Heritage Site. Kakadu is also gazetted as a locality, covering the same area as the national park, with 313 people recorded liv ...

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

. (ISBN corrected) (invalid, listed in publication).

Distribution and habitat

The northern river shark has been reported from

King Sound King Sound is a large gulf in northern Western Australia. It expands from the mouth of the Fitzroy River, one of Australia's largest watercourses, and opens to the Indian Ocean. It is about long, and averages about in width. The port town ...

, the

Ord River The Ord River is a river in the Kimberley region of Western Australia. The river's catchment covers . The lower Ord River and the conjunction with Cambridge Gulf create the most northern estuarine environment in Western Australia. The Ord ...

, and Doctors Creek near

Derby, Western Australia Derby ( ) is a town in the Kimberley region of Western Australia. At the 2016 census, Derby had a population of 3,325 with 47.2% of Aboriginal and Torres Strait Islander descent. Along with Broome and Kununurra, it is one of only three towns i ...

, the

Adelaide Adelaide ( ) is the capital city of South Australia, the state's largest city and the fifth-most populous city in Australia. "Adelaide" may refer to either Greater Adelaide (including the Adelaide Hills) or the Adelaide city centre. The dem ...

and

Alligator Rivers Alligator Rivers is the name of an area in an Arnhem Land region of the Northern Territory of Australia, containing three rivers, the East, West, and South Alligator Rivers. It is regarded as one of the richest biological regions in Australia, ...

in Australia's

, and the

Daru Daru is the capital of the Western Province of Papua New Guinea and a former Catholic bishopric. Daru town falls under the jurisdiction of Daru Urban LLG. The township is entirely located on an island that goes by the same name, which is loca ...

region and possibly the

Fly River The Fly River is the third longest river in the island of New Guinea, after the Sepik River and Mamberamo River, with a total length of and the largest by volume of discharge in Oceania, the largest in the world without a single dam in its catc ...

in Papua New Guinea. It inhabits large

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

, and coastal

bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a Gulf (geography), gulf, sea, sound (geography), sound, or bight (geogra ...

s, all of which are characterized by high

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can ...

, silty or muddy bottoms, and large tides. Young and juvenile sharks are found in fresh, brackish, and salt water (

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

ranging from 2 to 36 ppt), whereas adults have only been found in marine environments.

Description

Like other members of its genus, the northern river shark has a stocky body with a high back. The head is wide and flattened, with a broadly rounded snout and minute eyes equipped with

nictitating membrane The nictitating membrane (from Latin '' nictare'', to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. All ...

s. Each

nostril A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...

is divided into a very large incurrent opening and a small excurrent opening by a triangular skin flap. The sizable mouth is broadly arched, with short furrows at the corners. Thirty-one to 34 tooth rows are in the upper jaw and 30–35 tooth rows are in the lower jaw; the upper teeth are upright and triangular with serrated edges, while the lower teeth are narrower and straight to slightly curved. In the largest individuals, the first few lower teeth from the jaw median are spear-shaped with serrations near the tip. The

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s are large and broad, with gently backward-curving margins and pointed tips. The

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s are triangular with nearly straight trailing margins. The first

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

is long-based and triangular, with the apex almost forming a right angle; the second dorsal fin is some two-thirds as high as the first. The origin of the first dorsal fin lies over the pectoral fin insertions, while that of second dorsal fin lies over the pelvic fin rear tips. No ridge exists between the dorsal fins. The

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is smaller than the second dorsal fin and has a strong notch in the rear margin. The

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

has a strong lower lobe and a long, narrow upper lobe with a ventral notch near the tip. The

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as we ...

s are small, oval, and overlapping, bearing three horizontal ridges leading to marginal teeth. This shark is steel-gray above and white below; the color transition is sharp, located well below the eye, and becomes jagged on the sides of the trunk. The anal and caudal fins become dusky or black towards the trailing margins and tips. The maximum known length is . This species differs from 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 bein ...

(''G. glyphis'') in several morphological and

meristic Meristics is an area of ichthyology and herpetology which relates to counting quantitative features of fish and Reptile, reptiles, such as the number of fins or scales. A meristic (countable trait) can be used to describe a particular species of fi ...

characters, including having fewer

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

e (137–151 versus 213–222) and a lower, jagged gray-white color boundary.

Biology and ecology

With its slender teeth, small eyes, and high density of

ampullae of Lorenzini Ampullae of Lorenzini (singular ''Ampulla'') are electroreceptors, sense organs able to detect electric fields. They form a network of mucus-filled pores in the skin of cartilaginous fish (sharks, rays, and chimaeras) and of basal actinopterygia ...

, the northern river shark seems to be

adapted In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

for hunting

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

in conditions of poor visibility. In Doctors Creek, sharks may move to and from favored feeding areas with the tide.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 Heritage Trust, Murdoch University. Retrieved on 10 January 2010. Like other requiem sharks, this species is

, with the developing

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s forming a

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...

l connection to their mother after exhausting their supply of

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

. Females give birth around October, before the start of the

, on possibly a biennial cycle. One female examined contained nine

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal deve ...

es. The young are born at under long; males

mature Mature is the adjectival form of maturity, as immature is the adjectival form of immaturity, which have several meanings. Mature or immature may also refer to: * Mature, a character from ''The King of Fighters'' series *"Mature 17+", a rating in ...

between lengths of , while females mature between lengths of .

Human interactions

The northern river shark appears to be extremely rare, though more subpopulations may remain to be discovered in Australia and Papua New Guinea. Based on present information, no more than 250 mature individuals are estimated to exist in the wild, with no more than 50 in any particular subpopulation. This species is caught legally and illegally by

commercial fisheries Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often ...

using longlines and

gillnet Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

s, as well as by recreational fishers;

may pose a further threat to its survival. Because of its low natural abundance, limited distribution, stringent habitat requirements, and susceptibility to various human-caused threats, the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has assessed the northern river shark as Vulnerable. It has also been listed as endangered on the 1999 Commonwealth Environment Protection and Biodiversity Conservation Act, and on the 2000 Territory Parks and Wildlife Conservation Act. Kakadu National Park may be an important protected area for this species. No regulations restrict the capture of this species in Papua New Guinea.

References

{{Taxonbar, from=Q311339

northern river shark The northern river shark or New Guinea river shark (''Glyphis garricki'') is a species of requiem shark, in the family (biology), family Requiem shark, Carcharhinidae, found in scattered tidal rivers and associated coastal waters in northern Au ...

Freshwater fish of Australia Freshwater fish of New Guinea Freshwater fish of Papua New Guinea Brackish water organisms Fauna of the Northern Territory Critically endangered fish Critically endangered fauna of Oceania Critically endangered fauna of Australia Taxa named by Leonard Compagno Taxa named by Peter R. Last