Brown Smoothhound, Mustelus henlei
Brown Smoothhound, Mustelus henlei. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, June 2007. Length: 90 cm (2 feet 11 inches).
The Brown Smoothhound, Mustelus henlei, is member of the Hound Shark or Triakidae Family, and is known in Mexico as cazón hilacho. Globally, there are twenty-two species in the genus Mustelus, of which eight are found in Mexican waters, three in the Atlantic and five in the Pacific Ocean.
The Brown Smoothhound has an elongated slender body. They are copper-brown on their back and sides transitioning to white ventrally. Their fins have no distinguishing marks. The rear margins of their anal, caudal, and dorsal fins are dark. 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 2 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 above). The distance between the 2 dorsal fins is 19% to 24% of total body length. They have 5 gill slits with the last 2 being over the pectoral fins. They have skin denticles with 3 points on their flank.
The Brown Smoothhound is a coastal schooling pelagic demersal species found over the continental shelf and within enclosed bays and shallow muddy bottoms at depths up to 280 m (920 feet). They reach a maximum of 1.06 meters (3 feet 5 inches) in length. As of January 1, 2023, the International Game Fish Association world record stood at 2.95 kg (6 lbs 8 oz) with the fish caught in coastal waters off Long Beach, California in June 2012. 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, small fish, isopods, shrimp, squid, and polychaetes worms. 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 live pups that are 19 cm (7.5 inches) to 21 cm (8.5 inches) in length. They have lifespans of up to fifteen years.
The Brown Smoothhound is a resident of Mexican waters of the Pacific but 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, Sinaloa, southward 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).
From a conservation perspective the Brown Smoothhound has not been formally evaluated. They most likely have had population declines due to extensive commercial fishing pressures and low birth rates. They are considered to be a marginal food fish. They are marketed fresh, frozen, and smoked on a limited basis for human consumption. The preservation of Sharks in general is now a major focus of the Mexican Government with a moratorium having been put in place banning the retention of all sharks taken in Mexican waters. The Brown Smoothhound is a common component of public aquariums due to their small size and adaptability to captivity. This species is considered harmless to humans.