Atlantic Sharpnose Shark, Rhizoprionodon terraenovae
The Atlantic Sharpnose Shark, Rhizoprionodon terraenovae, whose common Spanish name is cazón de ley, is a member of the Requiem Shark or Carcharhinidae Family, known collectively as tiburónes gambuso in Mexico. This fish is named after its long snout. Globally, there are seven species in the genus Rhizoprionodon, three of which are found in Mexican waters, two in the Atlantic and one in the Pacific.
The Atlantic Sharpnose Sharks are medium-sized with slender bodies. They are grayish-brown dorsally, with more mature fish having small white spots on top, and transition to white ventrally. Their dorsal fins have black tips and their pectoral fins have white margins. The caudal fin margin in juveniles is black. Their anal fin has a slightly concave rear margin. Their caudal fin base has no keels but has notches above and below. Their first dorsal fin is moderate in height and originates in front of the pectoral fin rear edge with its center slightly closer to the pectoral fins than to the pelvic fins. Their second dorsal fin is small and very low; its origin is just behind the mid-point of the anal fin. Their pectoral fins extend to the middle of the dorsal fin. Their head has a long snout which is longer than the width of the mouth. They have long labial furrows at the corner of their mouth, large eyes, nictitating lower eyelids, and 24 or 25 rows of narrowly triangular, strongly oblique, and smooth to finally serrated teeth. They have five gill slits, the last two being over the pectoral fins.
The Atlantic Sharpnose Sharks are a very abundant small coastal shark found in the warm temperate and tropical waters of the western North Atlantic. They spend the majority of their time in shallow waters but migrate to deeper warmer waters during the winter months and can be found at depths up to 920 feet. They reach a maximum length of 1.10 meters (3 feet 7 inches). They forage in the surf zone and in estuaries, where they consume fish, crustaceans, and mollusks. In turn they are preyed upon by numerous large carnivorous fish including large sharks. They reach sexual maturity within three years. Reproduction is viviparous and follows an annual cycle with gestation periods of ten to twelve months. Litter sizes range from one to seven pups measuring 30 cm (12 inch) to 37 cm (16 inch). Larger females produce larger litter sizes but their pups are smaller in stature. Females reside in deeper waters most of the year and return to coastal waters in large sexually segregated schools to give birth. Nursery areas are inshore in enclosed bays and sounds. They have a lifespan of up to nine years.
In Mexican waters the Atlantic Sharpnose Sharks are found in all waters of the Atlantic.
The Atlantic Sharpnose Shark is most likely confused with the Caribbean Sharpnose Shark, Rhizoprionodon porosus (lacks white spots; only found along the east coast of the Yucatan in Mexican waters).
The Atlantic Sharpnose Sharks are caught in both commercial and recreational fisheries, as a by-catch in gill nets targeting other species and in shrimp trawl fisheries. In Mexico they are specifically and heavily targeted by artisanal fishermen utilizing gill nets and are being overfished with significantly diminishing populations. In the Southeastern United States they account for more than one-third of all landings of small coastal sharks with the majority caught in drift gill nets. Annual catch levels are on the order of 2.0 million fish per year, 88% by shrimp trawlers, 6% by commercial fishermen, and 6% by recreational anglers. Their meat is sold for human consumption and also used as chunk bait targeting other larger sharks. Their fins are small and not in demand for shark fin soup. In United States waters they are regulated with daily bag limits for recreational anglers and annual quotas for commercial fishermen. From a conservation perspective they are currently listed as of Least Concern but in Mexican waters should be considered Near Threatened. They are considered one of the most resilient sharks. As their nursery areas are located inshore, they are vulnerable to exploitation and human-induced habitat degradation. They pose a moderate threat to humans due to their inshore habitat bringing them in close contact with humans, however, their bites are normally not serious. They are the most common requiem shark in captivity and found in numerous public aquariums.
Atlantic Sharpnose Shark, Rhizoprionodon terraenovae, Juvenile. Fish caught from coastal waters off Jetty Park, Freeport, Texas, June, 2013. Length 33 cm (13 inches). Catch, photo, and identification courtesy of Kenneth Tse, Toronto, Canada.