Northern river shark

Northern river shark
Conservation status
	; Vulnerable (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Carcharhiniformes
Family:	Carcharhinidae
Genus:	Glyphis
Species:	G. garricki
Binomial name
	Glyphis garricki; Compagno, W. T. White & Last, 2008
	Range of the northern river shark

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

fresh and brackish water

Northern river sharks are likely

habitat degradation, this species has been assessed as Vulnerable by the International Union for Conservation of Nature

.

Taxonomy

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

East Alligator River, Kakadu National Park, Northern Territory.^[2]

Distribution and habitat

The northern river shark has been reported from

estuaries, and coastal bays, all of which are characterized by high turbidity, silty or muddy bottoms, and large tides. Young and juvenile sharks are found in fresh, brackish, and salt water (salinity ranging from 2 to 36 ppt), whereas adults have only been found in marine environments.^[2]^[3]^[4]

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 membranes. Each nostril 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. 31 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.^[2]

The

meristic characters, including having fewer vertebrae (137–151 versus 213–222) and a lower, jagged gray-white colour boundary.^[2]

Biology and ecology

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

viviparous, with the developing embryos forming a placental connection to their mother after exhausting their supply of yolk. Females give birth around October, before the start of the wet season, on possibly a biennial cycle. One female examined contained nine fetuses.^[3] The young are born at under 67 cm (26 in) long; males mature between lengths of 1.2 and 1.4 m (3.9 and 4.6 ft), while females mature between lengths of 1.4 and 1.7 m (4.6 and 5.6 ft).^[2]

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.

habitat degradation 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 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.^[1] No regulations restrict the capture of this species in Papua New Guinea.^[4]