Greynurse Shark, Carcharias taurus Rafinesque, 1810

Introduction

For many years, the Greynurse Shark was accused of being a 'maneater'. This is far from the truth.

3D interactive model of a Greynurse Shark

_{3D model of Greynurse Shark by cdmstudio.com.au}

Identification

The Greynurse Shark is a distinctive fish which is usually grey-brown on top and a dusky white underneath. Both dorsal fins and the anal fin are of a similar size.

Juveniles have reddish or brownish spots on the posterior (back) half of the body and tail. These spots often fade as the shark ages, but are sometimes still visible on adults.

Habitat

The Greynurse Shark lives in shallow coastal waters from the surf zone down to 60 m, although it has been recorded from water as deep as 190 m.

During the day, individuals are usually found in the vicinity of dropoffs, caves and ledges.

Distribution

The Greynurse Shark occurs in tropical and temperate waters in the Atlantic, Indian and western Pacific Oceans, although the species is known by different common names in different regions. It is recorded from all states of Australia except Tasmania.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Click on the map for detailed information.

Feeding and diet

Greynurse Sharks feed on fishes, which are pierced with the sharp teeth.

In some parts of the world, the species is known as the Spotted Ragged-Tooth. The reason for the this name is obvious. The species has fang-like teeth which are visible when the shark's mouth is closed. Greynurse Sharks are not however the 'maneaters' that some people have considered them to be.

The teeth of the Greynurse Shark are constantly being replaced. Older, damaged or blunt teeth on the exterior surfaces of the jaws are replaced by new teeth. In the whaler sharks, family Carcharhinidae, each tooth is replaced every eight to fifteen days.

The genus name Carcharias comes from the Greek carcharo, meaning sharp pointed or jagged, and refers to the impressive dentition.

Behaviours and adaptations

Life history

After fertilization, the developing young are enclosed in egg cases within each uterus of the female. They hatch from the egg cases at about 55 mm in length and then eat not only unfertilised eggs, but also their siblings. After about nine to twelve months two young are born, one from each uterus.

Greynurse Sharks are ovovivaparous. They produce eggs which hatch inside the female and have no placental connection. Other sharks such as the Port Jackson Shark lay eggs (oviparous sharks), or have a true placental attachment and give birth to live young (viviparous sharks), such as the Blue Shark.

The Greynurse Shark is not the only shark in which the young are oophagous (egg eaters). Others include the Shortfin Mako Shark and Porbeagle Shark.

Internal fertilization occurs in all sharks. Sperm transfer occurs through the claspers of the male.

Conservation

Pogonoski et. al. (2002), list the conservation status of the species as endangered.

Danger to humans

It is generally a slow-moving species that is not considered dangerous to people, although it should never be provoked by divers.