Brown Smoothhound, Mustelus henlei
The Brown Smoothhound, Mustelus henlei, whose Spanish common name is cazón hilacho, is member of the Hound Shark or Triakidae Family, known collectively as cazónes in Mexico. Globally, there are twenty two species in the genus Mustelus, eight of which are found in Mexican waters, three in the Atlantic and five in the Pacific.
The Brown Smoothhounds have elongated slender bodies. They are copper-brown on their back and sides transitioning to white ventrally. Their fins have no distinguishing marks. Their head is short with a pointed snout and large horizontal oval eyes. Their mouth is short and angular with the upper lip fold distinctly longer than the lower lip fold. The teeth are high, triangular, and pointed. Their nostrils are widely spaced. Their anal fin is smaller than and originates under the middle of the second of the two dorsal fins. Their caudal fin is strongly asymmetrical; the lower lobe is small with a concave rear edge. Their first dorsal fin is larger than the second dorsal fin; it is broadly triangular, originates closer to the pelvic fins than the large pectoral fins, and has a fibrous edge (pictured below). The distance between the two dorsal fins is 19% to 24% of total body length. The rear margins of their anal, caudal, and dorsal fins are dark. They have five gill slits with the last two being over the pectoral fins. They have skin denticles with three points on their flank.
The Brown Smoothhounds are a coastal schooling pelagic species found demersal over the continental shelf and within enclosed bays and shallow muddy bottoms at depths up to 920 feet. They reach a maximum length of 1.06 meters (3 feet 5 inches). They are an abundant species traveling in schools (at times with schools of Pacific Spiny Dogfish, Squalus acanthias and Leopard Sharks, Triakis semifasciata) or as solitary individuals. They feed on crabs, isopods, polychaetes worms, shrimp, squid, and a wide variety of small fish. In turn they are preyed upon by larger predatory bony fish including sharks, specifically the Sevengill Shark, Notorynchus cepedianus. Reproduction is viviparous with embryos being nourished by yolk-sac placenta. Litter sizes range from three to five pups born live and measuring 19 cm (7.5 inches) to 21 cm (8.5 inches). They have a lifespan of up to fifteen years. They are a poorly studied species and very little is known about their behavioral patterns.
In Mexican waters the Brown Smoothhound has a limited distribution being found along the entire west coast of Baja and throughout the Sea of Cortez; they are absent along the coast of the mainland from Mazatlán south to Guatemala.
The Brown Smoothhound Shark is most likely confused with the Gray Smoothhound, Mustelus californicus (first dorsal fin lacking fibrous edge and located further back on body), the Sharptooth Smoothhound, Mustelus dorsalis (sharp pointed teeth), the Sicklefin Smoothhound, Mustelus lunulatus (lower tail lobe expanded with strongly concave rear edge), and the Whitemargin Smoothhound, Mustelus albipinnis (fins with white edges).
The Brown Smoothhound are considered marginal food fish and normally a “catch and release”. They are marketed fresh, frozen, and smoked on a limited basis for human consumption. However, things have changed dramatically in Mexico over the last year. A shark in the possession of a local fishermen can be a real problem since a moratorium has been put in place banning the retention of all sharks taken in Mexican waters. They are caught fairly frequently by recreational anglers off Southern California. They are also a common component of public aquariums due to their small size and good adaptability to captivity. This species is considered harmless to humans. The Brown Smoothhound Sharks have has not been evaluated from a conservation perspective. They most likely have had population declines due to extensive commercial fishing pressures and low birth rates.