Humpback smoothhound (Mustelus whitneyi)

Spanish: Musola Prieta, Tollo Común
GenusMustelus (1)
SizeAdult length: 68 - 87 cm (2)
Length at birth: c. 25 cm (2)

The humpback smoothhound is classified as Vulnerable (VU) on the IUCN Red List (1).

A stocky-looking shark, the humpback smoothhound (Mustelus whitneyi) has a distinctively humped back, the shape of which gives this shark its name. The body is grey-brown above and much lighter below, and, unlike other members of the genus Mustelus, it has no spot or bar markings (2).

The humpback smoothhound’s mouth is angular and its teeth taper abruptly to a sharp point, making them ideal for crushing the shells and bones of its prey (2).

The fairly long head and snout of the humpback smoothhound make up roughly 25 percent of its total length. As with all members of the Mustelus genus, this species has two spineless dorsal fins, the second being almost as large as the first. The back edge of the second dorsal fin has a somewhat frayed appearance. There are few physical differences between the male and female humpback smoothhound, though the female tends to be slightly larger (2). 

The humpback smoothhound occurs along the Pacific South American continental shelf, where it is found just offshore from Peru to southern Chile (1) (2).

The humpback smoothhound is a bottom-dwelling species, and as such prefers the rocky sea floor where it can forage for prey (1). It is most commonly found at depths of 70 to 100 metres (2).

Very little biological information specific to the humpback smoothhound exists. It is known that it is a viviparous species giving birth to between 5 and 10 pups, which are normally around 25 centimetres long at birth. As with almost all sharks, the humpback smoothhound is carnivorous, feeding on crabs, shrimps and small bony fish. To date, there have been no studies into its behaviour or social interactions (2).

The humpback smoothhound’s numbers are decreasing. Although very few population studies have been conducted for this species, it is likely that the commercial fishing industry has played a significant role in its decline. As the humpback smoothhound is more common in the northern part of its range, the Peruvian fishery is considered to be the greatest threat to the survival of this species (1).

A legal catch size limit of 60 centimetres was introduced in Peru in 2001 for species of commercial fishing interest, which included the humpback smoothhound. However, the conservation benefits of this limit are disputed, as only juvenile humpback smoothhounds are protected (1).

Raising awareness of the fishing regulations and proper enforcement of the legal limits are needed if the humpback smoothhound is to be protected (1).

For more information on shark conservation see:

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  1. IUCN Red List (July, 2011)
  2. Compagno, L.J.V. (1984) Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date. Vol. 4: Part 2: Carcharhiniformes. Food and Agriculture Organization of the United Nations, Rome.