Florida Smoothhound, Mustelus norrisi
The Florida Smoothhound, Mustelus norrisi, whose common Spanish name is cazón viuda, is member of the Hound Shark or Triakidae Family, known collectively as cazones in Mexico. This fish is also known as the Narrowfin Smoothhound. Globally, there are 22 species in the genus Mustelus, of which eight are found in Mexican waters, three in the Atlantic and five in the Pacific.
The Florida Smoothhounds have elongated and slender bodies. They are uniform gray to gray-brown dorsally and transition to creamy white ventrally without additional spots or markings on their body. Some fish have fins with pale edges. In juveniles, the tips of the caudal and dorsal fins are dusky. Their head is short, narrow, and flattened ventrally. They have a short pointed snout, large oval eyes, and a prominent spiracle immediately behind each eye. Their mouth is long with the upper and lower lip folds being of equal length. Their teeth are low stumpy cusps set in 60 to 65 rows on the upper jaw and 55 to 60 rows on the angular lower jaw. Their nostrils are widely spaced. Their caudal fin is asymmetrical with a prominent hook and pointed lower lobe directed backwards. They have two large dorsal fins with rounded tips and concave rear margins: the first dorsal fin originates over or behind the rear base of the pectoral fins; the second dorsal fin, which is about 75% as high as the first dorsal fin, originates before the anal fin. Their anal and pelvic fins are much smaller than the second dorsal fin; their dorsal fins are falcate with serrated trailing edges; and their pectoral fins are small but long and thin with pointed tips. They have five gill slits with the last two located over the pectoral fins. They have overlapping single-pointed denticles with two converging ridges.
The Florida Smoothhounds are found inshore over sandy and muddy bottoms at depths up to 290 feet. They reach a maximum length of 1.10 meters (3 feet 6 inches) and weight of 13.8 kg (30.8 pounds). Females are generally larger than males. Depending on location they are either densely populated or sparse throughout their wide range and are known to segregate by size. They are migratory moving to inshore shallower waters during the winter months and returning offshore during the summer months. They feed on crabs, shrimp, and small fish. In turn they are preyed upon by the Blacktip Shark, Carcharhinus limbatus, the Dusky Shark, Carcharhinus obscurus, and the Great Hammerhead, Sphyrna mokarran. Reproduction is viviparous with embryos being nourished via a yolk sac then a yolk sac placenta while developing inside the mother’s body. Each litter yields 7 to 14 miniature adults which measure approximately 30 cm (12 inches) in length. They are a poorly studied species and very little is known about their behavioral patterns.
In Mexican waters the Florida Smoothhounds are found in all waters of the Atlantic.
The Florida Smoothhound is very similar to, and easily confused with, the Smooth Dogfish, Mustelus canis (much wider gap between nostrils; caudal fin with rounded lower lobe). It can also be confused with the Gulf Smoothhound, Mustelus sinusmexicanus (caudal fin lacking lower lobe). Based on genetic analysis, some believe the Florida Smoothhound and the Smooth Dogfish are one and the same species.
The Florida Smoothhounds 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. They are considered harmless to humans. From a conservation perspective, they are currently considered Data Deficient as their population trends are poorly documented. Although they have moderate fecundity levels, they are targeted by commercial fisherman at a small level. They are very accessible due to their inshore habitats and are a by-catch of the trawl industry at unknown levels. They are known to contain high levels of mercury. There is concern that they will follow in the footsteps of the Striped Smoothhound, Mustelus fasciatus, which has been fished to near extinction in southern Brazil due to intense gill net pressure on their inshore habitat.
Florida Smoothhound, Mustelus norrisi. Fish caught out of 450-foot water on the Golden Grounds, 150 miles west of Tarpon Springs, Florida, December 2013. Length: 1.37 meters (4 feet 6 inches). Catch, photo, and identification courtesy of George Brinkman, Guelph, Ontario, Canada.