Night shark
A deepwater requiem shark that migrates vertically and is prized for its fins.
The night shark (Carcharhinus signatus) is a requiem shark that lives in the Atlantic Ocean's temperate and tropical zones. It migrates vertically each day, staying deep during daylight and rising to shallower water after dark. This species typically grows to about 2 meters (6.6 feet) long, though the largest recorded individual reached 2.8 meters (9.2 feet) and 76.7 kilograms (169 pounds). It has a slender, streamlined body, a long pointed snout, and large green eyes when alive. Its upper side is dark grayish blue or brown, and its underside is white.
Night sharks are fast, schooling predators that hunt mainly small bony fish and squid, with most feeding happening at night. Like other requiem sharks, they are viviparous: females mate in summer and, after a year-long gestation, give birth to litters of usually 12 to 18 pups. This deepwater species is not considered dangerous to humans. It is caught incidentally by commercial tuna and swordfish longline fisheries in the western Atlantic, and also by a targeted longline fishery off northeastern Brazil. The shark is prized for its fins, and its meat, liver oil, and fishmeal are also used. However, most sharks caught off northeastern Brazil contain unsafe mercury levels.
Because of its low reproductive rate and documented population declines in areas like the Caribbean, the American Fisheries Society has assessed the night shark as vulnerable. A population assessment found the species is secure in U.S. waters, but this may not hold elsewhere.
The night shark was first scientifically described by Cuban zoologist Felipe Poey in 1868, based on a single set of jaws. He named it *Hypoprion signatus*. In 1973, Leonard Compagno moved it into the genus *Carcharhinus*. No type specimen has been designated. Its common name comes from the fact that it is mostly caught at night.
Its range spans the outer continental shelves and upper slopes of the Atlantic, from Massachusetts to Argentina in the west (including the Gulf of Mexico and Caribbean), and from Senegal to northern Namibia in the east. In U.S. waters, it is common off North Carolina and Florida, especially the Florida Straits, but rarer elsewhere. Reports from the Pacific coast of Panama are questionable. The night shark has been recorded as deep as 2 kilometers (1.2 miles), though it sometimes comes as shallow as 26 meters (85 feet).
Quick Facts
- Taxon
- Carcharhinus signatus
Facts from the source article.
Lore & Background
The night shark was first scientifically described by Cuban zoologist Felipe Poey in 1868, based on a single set of jaws, under the name Hypoprion signatus. In 1973, Leonard Compagno synonymized the genus Hypoprion with Carcharhinus. Its common name derives from the fact that it is mostly captured at night.
This slender, streamlined species has a long, pointed snout and large, green eyes when alive. It is dark grayish blue or brown above and white below. It inhabits the outer continental shelf and upper continental slope of the Atlantic Ocean, from Massachusetts to Argentina in the west and from Senegal to northern Namibia in the east. Off northeastern Brazil, large numbers congregate around seamounts of varying depths.
Night sharks are quick, nocturnally active, schooling predators that feed mainly on small bony fishes and squid. Reproduction is viviparous; females mate during the summer and give birth after a gestation period of a year. Males mature at about 1.8–1.9 m (5.9–6.2 ft) and 8 years of age, females at 2.0–2.1 m (6.6–6.9 ft) and 10 years. The maximum lifespan is estimated at 28 years for males and 30 years for females.
Reader's Guide
The night shark is caught incidentally by commercial tuna and swordfish longline fisheries in the western Atlantic, and also by a targeted longline fishery off northeastern Brazil. It is highly valued for its fins, which are exported for shark fin soup, and additionally used for meat, liver oil, and fishmeal. However, most sharks caught off northeastern Brazil have been found to contain unsafe concentrations of mercury.
Because of its low reproductive rate and historically documented declines in areas such as the Caribbean, the night shark has been assessed as vulnerable by the American Fisheries Society. A population assessment has indicated that this species is secure in the waters off the United States, but this may not be true elsewhere. This deepwater species is not known to pose a danger to humans. Its significance lies in its role as a bycatch species in major fisheries and the conservation concerns arising from its vulnerability to overfishing.
Did You Know?
- The night shark was first described by Cuban zoologist Felipe Poey in 1868.
- It conducts a diel vertical migration, spending the day at depths of 275–366 m and moving shallower than 183 m at night.
- Females give birth to litters of usually 12–18 pups after a gestation period of a year.
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