Student Stuff

Red Rockcod
Scorpaena cardinalis Richardson, 1842

A Red Rockcod at a depth of 10m, Fly Point, Nelson Bay, New South Wales, September 2003. View larger image.

A Red Rockcod at a depth of 12m, Fly Point, Nelson Bay, New South Wales, September 2003. View larger image.

Common name

Red Rockcod

Scientific name

Scorpaena cardinalis
scorpaena - sculpin (a type of fish) (Latin)
cardinalis - red (Latin). Refers to the colouration of this species.

Family name

Scorpaenidae
scorpaena - sculpin (a type of fish) (Latin)
idae - suffix meaning that this a family name. All animal family names end in -idae.

Size

The Red Rockcod is a member of the Scorpionfish family Scorpaenidae.

Scorpionfishes range in size from 7cm to 50cm in standard length (tip of snout to base of the tail fin - view glossary), but most are less than 30cm long.

The Red Rockcod grows to a maximum length of 40cm.

Number of species

The family Scorpaenidae is represented by about 350 species (70 genera) which occur in all tropical and temperate seas. Eighty species (33 genera) are recorded from Australia. Twelve species in the genus Scorpaena have been recorded in Australian waters, two of which have been recorded in the Sydney region, the Red Rockcod, and the Southern Rockcod, Scorpaena papillosus. The two species differ in the number of pectoral fin rays and lateral line scales.

The family contains some of the most beautiful, ugly, and deadly of fishes. Examples include the beautiful Red Firefish, Zebra Lionfish, Weedy Scorpionfish and the strange Demon Stingerfish which walks along the bottom on finger-like appendages. The related family Synanceiidae contains the deadly Reef Stonefish which has potentially lethal poison injected via the dorsal spines.

There is no comprehensive work on the scorpionfishes of Australia. Much work still needs to be done on the taxonomy of this family.

Distribution

Scorpionfishes are mostly bottom-dwelling fishes that are found worldwide in all but the coldest oceans.

The Red Rockcod is found in temperate waters of eastern Australia, ranging from southern Queensland to eastern Victoria.

View a map of the collecting localities of specimens in the Australian Museum Fish Collection.

A Red Rockcod at Shark Point, Sydney, New South Wales.

Habitat requirements

Scorpionfishes can be found in marine, estuarine and even fresh waters. Some species, such as the Idiotfishes (subfamily Sebastalobinae) are found on the deep ocean floor down to 2200m. Others, like those in the subfamily Setarchinae, swim in the oceanic midwaters. Most species, however, live in coral or rocky reefs.

The Red Rockcod is often found with sponges and in rocky areas covered with algae.

Structural, physiological and behavioural adaptations

The Red Rockcod has a number of interesting adaptations that include venomous dorsal spines, a large mouth and complex colouration.

The venomous dorsal fin spines of a Red Rockcod from the Australian Museum Fish Collection.

The head of a Red Rockcod at a depth of 18m, Dee Why, Sydney, New South Wales, November 2002. Note the mottled pattern and skin filaments. View larger image.

A juvenile Red Rockcod showing the large mouth of this species.

The suborbital stay (see arrows) of a Red Rockcod.

Venomous Dorsal fin spines

The twelve dorsal spines of the Red Rockcod are toxic. A sting from a Red Rockcod can be excruciatingly painful, and last for half a day. The poison is denatured (glossary) by heat so immersing the affected area in very hot water is the best first aid before consulting a doctor.

Some scorpionfishes, such as the stonefishes are extremely toxic and have caused human fatalities.

Colouration

Many scorpionfishes have cryptic colouration. This is is an advantage for predatory fishes like the Red Rockcod that often lie motionless on the bottom. The Red Rockcod's colouration is highly variable from light grey to bright red with blotches. The chest usually has small dark spots.

This species has skin flaps on the head, lateral line and other parts of the body. These help to disguise the shape of the fish. View images of a camouflaged scorpionfish in the Solomon Islands (image 1, image 2).

Large mouth

The Red Rockcod is a predatory fish with a big mouth. It often lies motionless on the bottom waiting for passing prey of small fishes and invertebrates.

This species swallows its prey whole, so within reason, the bigger the mouth, the larger the prey item that can be consumed.

Suborbital stay

Scorpionfishes are all characterised by a bony strut (the suborbital stay) running below the eye.

In fishes such as the Ocean Perch (view fact sheet) this is a smooth ridge. In others, (including the Red Rockcod), the suborbital stay has developed into a raised row of spines. The function is unclear, but in many species it may help protect the eyes.

Follow-up questions

The family Scorpaenidae is classified within the order Scorpaeniformes. Name two other families within the order Scorpaeniformes. (View the list of fact sheets by scientific name)
The scorpionfishes are related to the families Platycephalidae and Hoplichthyidae. What are the common names for fishes in these families? (Examples of these families are also on the Australian Museum fish website.)
Most scorpionfishes are marine, but some species live in brackish, or even freshwater. One species is regularly found in freshwater from northern Queensland to southern New South Wales. Which species is it? (view fact sheet)