The Houndsharks or Triakidae is one of the largest families of sharks, with more than 40 species in 9 genera (In some classifications, the family is split into two subfamilies, with Mustelus, Scylliogaleus, and Triakis in the subfamily Triakinae, and the remaining genera in the subfamily Galeorhininae.).
They are distributed worldwide in warm to temperate coastal seas. Most species can be found in continental or insular waters, from the shoreline and intertidal zone to the outermost shelf. They are often found close to the bottom in sandy, muddy and rocky inshore habitats, near river mouths or enclosed bays. There are a few deep-water species that inhabit the continental sloped down to depths greater than 6,562 feet. Many of these sharks are endemic, with a restricted distribution and range.
Triakidae range in size from small to medium, with two medium-sized spineless dorsal fins. The first dorsal fin is well ahead of the pelvic fin bases, and the anal fin. The eyes are cat-like, horizontally oval, with nictitating membranes. There are no nasoral grooves. The anterior nasal flaps are not barbel-like, with the exception of genus Furgaleus. The mouth is long, arched and angular, and reaches pas the front of the eyes. There are labial furrows that are of moderate size to very long. The caudal fin does not have a strong ventral lobe or lateral undulations on its dorsal margin. Some of the members of this family, like Mustelus are extremely hard to identify. The only reliable way would be by vertebral counts.
Many members of this family are strong, active swimmers, and almost swim continuously. Some members of this family rest on the bottom. Many do swim close to the seabed. Some Houndsharks are active during the day, and others are nocturnal, being active during night. Triakidae are either ovoviviparous or viviparous. The viviparous species have a yolk sac placenta, having 1 to 2 pups per litter, to as many as 52 pups per litter. Some of the smaller coastal species reproduce quickly.
Feeding typically happens on the bottom and midwater, on invertebrates and bony fish. There are some that will eat large crustaceans primarily, and others that will feed primarily on cephalopods.
Most of these sharks are fairly common and abundant. Galeorhinus and Mustelus are fished heavily for their find, liver oil and meat. The species that reproduce quickly are less susceptible to fishing pressures. There are several rare species that do not experience the same. This family of sharks is not a threat to humans.
Caribbean Smoothhound– Mustelus insularis (Heemstra, 1997)
Kermadec Smoothhound– Mustelus sp. not yet described
Sarawak Smoothhound– Mustelus sp. not yet described