Prickly Dogfish, Oxynotus bruniensis (Ogilby, 1893)

Introduction

The Prickly Dogfish has a hump-backed body which has a flat lower surface and very rough skin. In Australia, the species occurs the central New South Wales coast to the Great Australian Bight, including Tasmania.

3D interactive model of a Prickly Dogfish

_{3D model made by cdmstudio.com.au}

Identification

The Prickly Dogfish has a hump-backed body with a flat lower surface. The body is nearly triangular in cross-section. The species has prominent abdominal ridges, two sail-like dorsal fins which are each preceded by a spine, and lacks an anal fin.

It is brown to grey in colour, although the dorsal fins and posterior margins of the pectorals and pelvics are often translucent to white. The skin of the Prickly Dogfish is very rough, giving rise to the common name. The denticles (modified scales) are incredibly rough and are elongate with a blade like cusp.

Habitat

The Prickly Dogfish occurs in deepwater temperate marine waters on outer continental and insular shelves and upper slopes from from 45 m to 1067 m. They are most commonly found between 350-650 m.

Distribution

In Australia, the Prickly Dogfish is widespread from Southern Queensland to west of the Great Australian Bight. It is also found in the Tasman Sea and throughout New Zealand.

Worldwide, there are five species in the Family Oxynotidae. Only one species is known from Australia.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Source: Atlas of Living Australia.

Feeding and diet

The Prickly Dogfish has short, snout, lanceolate (spear or lance-shaped) teeth in the upper jaw, and blade-like teeth in the lower jaw. This arrangement of teeth and the fleshy lipped mouth bears some resemblance to the Cookiecutter Shark.

They are carnivorous and feed exclusively on egg capsules of Chimaeras (Ghost Sharks). Finucci (2016) stated "DNA sequences has revealed that O. bruniensis preys on the egg cases of holocephalans, including the Pacific spookfish (Rhinochimaera pacifica) and the brown chimaera (Chimaera carophila), besides the longnose chimaera (H. raleighana)."

Reproduction

Prickly Dogfish are born at approximately 24 cm and males mature at ~55cm TL while females mature at ~64 cm TL. They are aplacental viviparious (give birth to live young that develop from eggs in the female) and produce ~8 pups per litter.

Behaviours and adaptations

Fishes which swim in open water are often spindle-shaped (fusiform, meaning tapering to both ends). This is the most energy efficient body shape for pelagic fishes.

For fishes that live on or near the bottom, a spindle-shaped body is less energy efficient (Pridmore & Barwick, 1993). These fishes (the Prickly Dogfish included) often have cambered (humped) body shapes. They are often taken as by catch in trawls.