Sicklefin Smoothhound, Mustelus lunulatus
Sicklefin Smoothhound, Mustelus lunulatus. Fish caught out from coastal waters off Puerto Los Cabos, Baja California Sur, July 2007. Length: 1.00 m (3 feet 3 inches).
The Sicklefin Smoothhound, Mustelus lunulatus, is a member of the Hound Shark or Triakidae Family, and is known in Mexico as cazón segador. Globally, there are twenty-two species in the genus Mustelus, of which eight found in Mexican waters, three in the Atlantic and five in the Pacific Ocean.
The Sicklefin Smoothhound has an elongated slender body. They are gray or brown on their backs and sides transitioning to white ventrally. Their fins have no distinguishing marks. Their head has a pointed snout, large horizontal oval eyes, and a large mouth. Their teeth are distinctive and only feature small nubs. They have prominent short spiracles behind each eye. 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 with an expanded lower lobe and a concave rear edge; their first dorsal fin is slightly larger than the second dorsal fin with a concave rear edge and a base midway between the pectoral and pelvic fins; and, the origin of the second dorsal fin is well before the origin of the anal fin. They have 5 gill slits with the last 2 being over the pectoral fins. They have skin denticles shaped as pointed ovals with a single point.
The Sicklefin Smoothhound is a coastal schooling pelagic species found demersal over the continental shelf and within enclosed bays and shallow muddy bottoms at depths up to 200 m (655 feet). They reach a maximum of 1.75 m (5 feet 9 inches) in length. They feed on crabs, fish, isopods, shrimp, squid, and polychaetes worms. In turn they are preyed upon by larger predatory bony fish including sharks. Reproduction is viviparous with embryos being nourished by yolk-sac placenta. Litter sizes are small with pups born live. The Sicklefin Smoothhound is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
The Sicklefin Smoothhound is a resident of all Mexican waters of the Pacific Ocean.
The Sicklefin Smoothhound is most likely confused with the Brown Smoothhound, Mustelus henlei (first dorsal fin with a fibrous edge), the Gray Smoothhound, Mustelus californicus (broadly triangular dorsal fin), the Sharptooth Smoothhound, Mustelus dorsalis (sharp pointed teeth), and the Whitemargin Smoothhound, Mustelus albipinnis (fins with white edges).
From a conservation perspective the Sicklefin 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. This species is considered harmless to humans.