Bignose Shark, Carcharhinus altimus
The Bignose Shark, Carcharhinus altimus, whose common Spanish name is tiburón narizón, is a member of the Requiem Shark or Carcharhinidae Family, known collectively as tiburónes gambuso in Mexico. In the greater Los Cabos area, this fish is known as tiburón colorado, due to its reddish belly. Globally, there are 35 species in the genus Carcharhinus, 17 of which are found in Mexican waters, seven in the Atlantic, four in the Pacific, and six in both oceans.
The Bignose Sharks are heavily built with a long, broad, bluntly-pointed to rounded snout, which gives rise to their common name. They are gray and have no prominent markings other than being white with red tinges ventrally and having black tips on the corners of their pectoral fins. Their head has an overhanging snout, moderately large circular eyes with nictitating membranes, prominent well-developed triangular nasal skin flaps, and a broadly curved mouth that lacks obvious furrows at the corners. They are equipped with triangular upper teeth and tall narrow lower teeth with serrated edges. Their upper jaw has 14 to 16 teeth on each side and their lower jaw has 14 or 15 teeth on each side. They have five pairs of moderately long gill slits, the last two originating over the pectoral fin base. Their caudal fin has a large lower lobe with a strong ventral notch near the tip of the upper lobe. Their first dorsal fin originates over the rear of the pectoral fin base and is large, fairly tall, and sickle-shaped with a blunt apex and a long free rear tip. Their second dorsal fin is slightly ahead of the anal fin and is relatively large with a short free rear tip. There is a high conspicuous ridge between the dorsal fins. Their pectoral fins are long and wide with straight margins and pointed tips.
The Bignose Sharks are a circumglobal species found in tropical and warm waters ranging from the edges of the continental shelf and insular slopes. They are found from the surface to depths of 1,410 feet. Male Bignose Sharks are slightly larger than females reaching a maximum length of 2.8 meters (9 feet 2 inches) and a recorded weight of 168 kg (370 pounds). They are bottom dwellers that migrate vertically at night to shallower depths. They are known to make seasonal migrations of 1,000 to 2,000 miles to cooler waters during the summer and to return in the fall. They are voracious predators feeding on various fish, rays, sharks, as well as crabs, lobsters, octopus, and shrimp. Juveniles are preyed upon by various sharks including the White Shark. Reproduction is long and sexual maturity is not reached, on average, until 21 years. They are viviparous with 10-month gestation periods and litter sizes of 3 to 15 pups. At birth, the pups measure between 61 cm (2 feet) and 91 cm (3 feet) in length and are immediately capable of caring for themselves.
In Mexican waters the Bignose Sharks are found in all waters of the Atlantic and the Pacific.
The Bignose Sharks is most likely confused with the Night Shark, Carcharhinus signatus (long second dorsal fin; green eyes) and the Sandbar Shark, Carcharhinus plumbeus (small eyes; poorly developed nasal flaps; very tall first dorsal fin).
The Bignose Sharks are caught primarily as a by-catch of deep water trawlers, deep water longline fishermen targeting tuna, and gill nets. They are rare catches by hook and line. They are utilized in some cultures for their meat, fins, skin, and liver oil. Although very large in stature they are not considered to be a threat to humans due to their deep water habitat. In United States waters, they are heavily regulated and their harvest or possession has been banned. Bans are also in place in Australia, Brazil, and Europe but these only cover a limited geographic area of their total range. From a conservation perspective they are listed as Data Deficient globally suffering from misidentifications and poor catch data. In certain parts of the world (Northwest Atlantic) they are classified as Near Threatened and in locations where they are not fished commercially (Australia) as of Least Concern.
Bignose Shark, Carcharhinus altimus. Access to fish for photographic purposes provided the commercial fishermen of the Greater Los Cabos area, Baja California Sur, January 2013. Length: 1.5 meters (5 feet). Weight: 45 kg (100 pounds).