Rock salmon refers to either of two kinds of fish:

The first, also called rock eel, flake

Flake (fish)

Flake is a term used in Australia to indicate the flesh of any of several species of small shark, particularly Gummy shark. The term probably arose in the late 1920s when the large-scale commercial shark fishery off the coast of Victoria was established. Until that time, shark was generally an...

, and huss in the UK, is any one of many species of small shark, including the spiny dogfish

Spiny dogfish

The spiny dogfish, spurdog, mud shark, or piked dogfish, Squalus acanthias, is one of the best known of the dogfish which are members of the family Squalidae in the order Squaliformes. While these common names may apply to several species, Squalus acanthias is distinguished by having two spines ...

 (Squalus acanthias) or the bull huss

Nursehound

The nursehound , also known as the large-spotted dogfish, greater spotted dogfish, or bull huss, is a species of catshark, family Scyliorhinidae, found in the northeastern Atlantic Ocean. It is generally found amongst rocks or algae at a depth of...

 (Scyliorhinus stellaris).

Rock salmon is consumed in many European countries and is often sold by fish and chip shops in the UK. However, the spiny dogfish is now an endangered species due to overfishing

Overfishing

Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....

, and is classed as Vulnerable on the IUCN Redlist and the North East Atlantic population as Critically Endangered.

The second is the mangrove red snapper

Mangrove red snapper

Commonly called Mangrove Jack within Australia, the Mangrove red snapper is an explosive and powerful sport fish that is renowned for its superb eating and fighting qualities....

 or mangrove jack, Lutjanus argentimaculatus, family Lutjanidae

Lutjanidae

Snappers are a family of perciform fish, mainly marine but with some members inhabiting estuaries, feeding in freshwater. Some are important food fish. One of the best known is the red snapper....

.