Crocodile Shark

The crocodile shark is the sole member of the family Pseudocarchariidae. This small mackerel shark travels from the mesopelagic depths during the day to shallow waters at night to feed. Crocodile sharks measure less than 3.3 feet long and rank as the smallest mackerel shark species. They pose little threat to humans and garner little to no interest from commercial fisheries. 

5 Crocodile Shark Facts

• They possess large eyes equipped with reflective green or yellow retinas that allow them to easily see in the dark. 
• When actively pursuing fish and other prey, they will breach the surface of the water to chase after food. 
• Females typically give birth to four live pups, which are oophagous until they are born. 
• They possess large livers that make up around a fifth of their total body weight. 
• In 1985, they damaged deep-sea fiber optic cables installed by AT&T near the Canary Islands. 

Classification and Scientific Name

The scientific name of crocodile sharks is Pseudocarcharias kamoharai, and they belong to the mackerel shark order Lamniformes. Other well-known mackerel sharks include the goblin shark, the megamouth shark, and the great white. The word Lamniformes derives from the Ancient Greek word lamna, meaning “a kind of shark,” and the Latin iformes, meaning “shaped” or “appearance.” 

They are the sole extant member of the family Pseudocarchariidae. Its family name derives from the Greek words pseudo, meaning “false” or “pretend,” and karcharos, meaning “a kind of shark.” Roughly translated, its family name means “pretender shark” or “false shark.” Meanwhile, its specific name, kamoharai, honors the Japanese ichthyologist, Toshiji Kamohara. Kamohara was a fish expert who worked at Kochi University and discovered many novel species during the early and mid-20th century.

Its common name stems from a Japanese word, mizuwani. Translated into English, its name means water (mizu) crocodile (wani). Its name refers to its sharp teeth and habit of biting aggressively at prey above the surface of the water like a crocodile. They also have several other common names, including the water crocodile, the Japanese ragged-tooth shark, and Kamohara’s sand shark. 

Appearance

They feature elongated, slender bodies with short heads and pointed snouts. The body looks dark gray-brown on the dorsal (top) side and lighter on the ventral (bottom) side. Their large, reflective eyes can appear either green or yellow. They sport five pairs of gill slits and large, arched jaws equipped with up to 30 tooth rows on both jaws. Crocodile sharks have small, rounded pectoral fins and pelvic fins around the same size as the pectoral fins. The dorsal fin also measures quite small, and the caudal fin appears asymmetrical. At maximum size, crocodile sharks measure around 3.6 feet long and weigh between 8.8 and 13.2 pounds. 

Distribution, Population, and Habitat

In the Atlantic, you can find them from the coasts of Brazil to western and southern Africa. In the Indian Ocean, they range from the shores of Madagascar to the Bay of Bengal on the eastern coast of India. Meanwhile, in the Pacific Ocean, crocodile sharks occur around Japan, Korea, and Taiwan in the north and as far south as Australia and New Zealand. 

Generally speaking, crocodile sharks prefer waters where the average surface temperature is 68 degrees Fahrenheit. Based on these temperatures, they don’t cross the boundaries of 37 degrees north or 44 degrees south. Crocodile sharks dwell in the pelagic zones at depths of around 1,940 feet below sea level. However, they regularly travel to shallower waters to feed. Rather than having a widespread distribution, crocodile sharks tend to live in high densities within narrow ranges. This evidence implies that they do not migrate, or at the very least, that they migrate only short distances. 

Predators and Prey

Currently, scientists do not know of any organisms that actively prey on adult crocodile sharks. That said, crocodile sharks live at extreme depths, which makes studying them difficult. The oceans may house some unknown predator that preys on small or juvenile crocodile sharks. 

Their diet consists mostly of medium-sized bony fish, squid, and shrimp. Crocodile sharks spend their days at mesopelagic depths and travel closer to the surface at night to feed. They rely on their excellent eyesight to help them find prey in the dark water. Experts speculate that crocodile sharks actively pursue their prey rather than relying on ambush tactics or stealth. This theory stems from the fact that they possess large, muscular tails suited for active pursuit and the documented behavior of captured crocodile sharks. For example, eyewitnesses report seeing crocodile sharks jumping out of the water in pursuit of low-flying bats.

Reproduction and Lifespan

Little is known about their reproduction. It does not appear that crocodile sharks breed during a specific season. We also do not know how long the gestation period lasts for females, although most experts estimate that it is long. Females give birth to an average of 4 live offspring known as pups. While in utero, the crocodile shark embryos feed on egg capsules developed by their mother until they are born. Males reach sexual maturity at 29 to 42.5 inches long, while females reach maturity at 35 to 40 inches long. Their lifespan remains unknown. 

Food and Cooking

Commercial fisheries often catch crocodile sharks with pelagic longlines, squid jigs, and tuna gillnets. These fishing operations normally use such technologies to catch swordfish and tuna. However, due to their small size and low-quality meat, most fishing boats simply throw any caught crocodile sharks back into the sea. While you can cook and eat crocodile shark, its unappetizing flavor means it does not feature prominently in any regional cuisine. 

Population

The crocodile shark enjoys a circumpolar distribution. While it is susceptible to overharvesting due to its low reproductive rate, this does not appear to be the case. This likely stems from the fact that commercial fisheries do not actively target crocodile sharks due to their low-quality meat. Given these factors, their population is currently stable, or at least not rapidly decreasing. The IUCN presently classifies them as a species of Least Concern. However, accurate population data does not exist due to their bottom-dwelling habits.