Night Shark

Night sharks are requiem sharks living in the Atlantic Ocean. They are characterized by their green eyes, though they lose this color after death.

Night Shark Scientific Classification

Kingdom Animalia
Phylum Chordata
Class Chondrichthyes
Order Carcharhiniformes
Family Carcharhinidae
Genus Carcharhinus
Scientific Name C. signatus

Description

Generally, night sharks are 6.6 ft long, but the current record-holding specimen is 9.2 ft long and weighs 169 lbs. These sharks are slender, with large circular eyes and nares covered with skin flaps. There are 15 rows of teeth on both jaws, with those on the upper jaw being either smooth or serrated and those on the lower one being more smooth-edged.

The pectoral fins are the longest fins of this shark, around less than a fifth of its total length. The dorsal fins are tiny, with the second being smaller than the first. Night sharks are grayish blue or brown with scattered black spots when observed from above and are much lighter when viewed from below.

Where do they live

Night sharks have been spotted throughout the Atlantic Ocean, from Massachusetts in the U.S. to Argentina in the west to Namibia and Senegal in the east.

As a deepwater shark, it generally lives at depths of 125-1970 ft but has been observed at depths as low as 6336 ft and in waters close to the surface, about 85 ft deep.

Behavior

Hunting

This shark’s nocturnal feeding habits give it its common name. Its diet consists mainly of small bony fish like butterfish, flying fish, mackerel, mullet, and seabass but will also go after squids and shrimp if available.

Social

Night sharks move about in schools, though reports indicate that pregnant or ovulating females separate themselves from groups for some reason.

Migratory

Like many deep sea creatures, these sharks appear to perform diel vertical migration, i.e., diurnally remaining at depths of 902–1,201 ft and coming up to about 600 ft at night.

Reproductive

Similar to other requiem sharks, they give birth to a litter of 4-18 live pups. The newborn pups are 20–28 inches long and grow rapidly, so they can take care of themselves during this time.

Males become sexually mature at eight years when they are around 6 ft tall, while females do so a bit later at ten years at about 7ft. Female night sharks also tend to live longer, up to 30 years, while males generally live up to 28 years.

Adaptations

These sharks have excellent vision for life in the depths due to their big green eyes.

Interactions with humans

While this shark is often caught for its meat or as bycatch alongside swordfish and tuna, the higher levels of mercury inside their bodies mean consuming them on a regular basis becomes risky.

The IUCN labels the night shark as “Endangered” or “EN”, due to its low reproductive rate and tendency to be caught as bycatch, as mentioned above, with juveniles particularly vulnerable. In 1997, the U.S. agency NOAA’s National Marine Fisheries Service classified the night shark as a “Species of Concern”, with a 2003-2008 study indicating that the population has stabilized in U.S. waters.

Sources

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