Bignose Shark

The bignose shark, scientifically known as Carcharhinus altimus, is a species within the requiem shark family, Carcharhinidae. This species is widely distributed across tropical and subtropical regions globally and is known for its migratory behavior, often inhabiting deep waters along continental shelf edges. Typically residing at depths ranging from 90 to 430 meters, the bignose shark occasionally migrates toward the surface or shallower waters during the night. A plain-colored species, it can reach lengths of 2.7 to 2.8 meters. Distinctive features include its long, broad snout adorned with pronounced nasal flaps, tall triangular upper teeth, and long, nearly straight pectoral fins. A notable ridge is present between its two dorsal fins.

Feeding primarily on bony and cartilaginous fishes and cephalopods, the bignose shark is an adept hunter near the seafloor. It exhibits viviparous reproduction, with embryos receiving sustenance through a placental connection, and females give birth to litters of three to fifteen pups following a gestational period of approximately ten months. Although its size suggests potential danger, this shark inhabits depths that largely preclude interactions with humans. However, it is often caught as bycatch by commercial fisheries, with its body parts—meat, fins, skin, liver oil, and offal—being utilized. The species faces pressure from fishing across its range, raising concerns due to its slow reproductive rate. Evidence suggests a decline in populations within the northwestern Atlantic and other areas.

Originally described as Eulamia altima by shark expert Stewart Springer in a 1950 edition of American Museum Novitates, the species was later reassigned to the genus Carcharhinus. The epithet "altimus" is derived from the Latin "altus," meaning "deep," reflecting its deepwater habitat preference. The type specimen, an immature female measuring 1.3 meters in length, was captured near Cosgrove Reef in the 🇺🇸 Florida Keys on April 2, 1947. Additionally known as Knopp's shark among 🇺🇸 Florida fishery workers before its formal description, the bignose shark is considered to have a circumglobal presence in tropical and subtropical marine environments.

In the Atlantic Ocean, the species is found from Delaware Bay to 🇧🇷 Brazil, in the Mediterranean Sea, and along the West African coast. Its 🌊 Indian Ocean range includes 🇿🇦 South Africa, 🇲🇬 Madagascar, the 🌊 Red Sea, 🇮🇳 India, and the 🇲🇻 Maldives. Recorded sightings in the 🌊 Pacific Ocean span from 🇨🇳 China to 🇦🇺 Australia, around Hawaii (🇺🇸 United States), and from the Gulf of 🇺🇸 California to 🇪🇨 Ecuador. Common occurrences have been noted off the coasts of 🇺🇸 Florida, the 🇧🇸 Bahamas, and the West Indies, while it remains rarely observed off 🇧🇷 Brazil. The species has become more prevalent in the southwestern Mediterranean Sea.

Predominantly residing near continental shelf edges and over upper continental slopes, the bignose shark is known to swim close to the sea floor. Juveniles may venture into shallower waters up to 25 meters deep. Observations of the species nearing the surface during nighttime suggest diel vertical migration patterns. In the northwestern Atlantic, this species undergoes a seasonal migration, spending summers off the US East Coast and winters in the 🌊 Gulf of Mexico and the 🌊 Caribbean Sea. Some individuals have been recorded traveling distances between 1,600 and 3,200 kilometers.

The bignose shark is characterized by a sturdy build, with a long, broad, and blunt snout featuring well-developed triangular skin flaps near the nostrils. Its moderately large, circular eyes come equipped with protective nictitating membranes. The mouth displays a broad curve without prominent furrows at the corners. The upper and lower jaws comprise 14 to 16 and 14 to 15 rows of teeth, respectively, featuring serrated cusps. The species' five pairs of moderately long gill slits, long and wide pectoral fins with pointed tips, and nearly straight margins are distinct anatomical features. A high midline ridge runs between the dorsal fins, and the caudal peduncle possesses a crescent-shaped notch at the upper caudal fin's origin. Bignose sharks exhibit gray to bronze coloration above, with a faint pale stripe along the flank and a white underside. Occasionally a green sheen appears near the gills, and young sharks display darker fin tips. These sharks can grow to at least 2.7 meters for males and 2.8 meters for females, with a potential maximum length of 3 meters and a recorded maximum weight of 168 kilograms.

Feeding primarily on bottom-dwelling bony and cartilaginous fishes, including lizardfishes, croakers, flatfishes, and batfishes, as well as cephalopods, juvenile bignose sharks may become prey to larger predators. This species is viviparous, with embryos transitioning from yolk sac nutrition to a placental connection for nourishment from the mother. Females generally bear litters of three to fifteen pups, with a gestation period lasting approximately ten months. Birthing occurs in varying months depending on the region, with newborns measuring 70 to 90 centimeters. Maturity in males and females is reached at lengths of around 2.2 and 2.3 meters, respectively, with the average reproductive age being 21 years.

Though it could pose a threat due to its size, the bignose shark's preference for deep waters minimizes human interactions. It is frequently caught incidentally in gillnets, bottom trawls, and deep-set pelagic longline fisheries, which often target tuna. Regularly captured in Cuban waters, it is processed for liver oil, shagreen, and fishmeal. In Southeast Asia, the meat is consumed, and the fins are shipped to East Asia for shark fin soup. Within the 🇺🇸 United States, the bignose shark is classified under the 2007 Fishery Management Plan for Atlantic tunas, swordfish, and sharks as a Prohibited Species and is not commercially utilized. Similar regulations exist in 🇦🇺 Australia.