Species Profile: The Crocodile Shark

A crocodile shark

A Group Of Crocodile Sharks

The crocodile shark is a pelagic shark (open-ocean shark) that got its name for its characteristic vigorous and continuous snapping when it’s caught or handled. They live well away from land in the tropical and sub-tropical waters of all oceans worldwide.

It has a gray, distinctly slender body with a paler underbelly, white-tipped fins and some individuals display white spots on their body. The eyes are huge, and the fins small. Its jaw is highly protusible and powerful with a wide mouth and long, slender teeth.

1. Scientific Name

Pseudocarcharias kamoharai

2. Scientific Classification

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Chondrichthyes
  • Order: Lamniformes
  • Family: Pseudocarchariidae
  • Genus: Pseudocarcharius
  • Species: Pseudocarcharias kamoharai

3. Life Expectancy

Unknown.

There is presently no data on the lifespan or age at maturity for either sex of this species of shark.

4. Average/Maximum Length

It is the smallest of mackerel fish. The male of the species mature averagely at about 74 cm (2.4 feet), while females mature at a length of 90 to 100 cm (2.9 to 3.3 feet). The maximum length recorded so far is 110 cm (3.6 feet).

5. Average/Maximum Weight

Between 4 to 6 kg (9 to 13 lbs.).

6. Maximum Swimming Speed

The crocodile shark is a fast and active swimmer but there is no documented record of its actual swimming speed in the wild.

7. Danger To Humans

There is no documented evidence or report of the crocodile shark attacking humans. Also, it’s generally considered as harmless to people owing to its relatively small size. However, it has very strong jaws and pointed teeth so it should be handled with care because it snaps quickly, strongly and vigorously to free itself when captured.

8. Reproduction Details

Crocodile sharks are ovoviviparous with uterine oophagy. The more developed embryos will feed on other eggs while in the womb. Each litter produces about 4 pups with 2 pups in each uterus. Newly born pups measure from 40 cm (16 in.) and above. There is no information on their mating season/habits and nursery grounds.

9. Diet/Hunting Habits Of The Crocodile Shark.

By examining the stomach contents of crocodile sharks, researchers noticed that it consumes bristlemouths, squid, lanternfishes, and shrimps. Its firm muscular body, dentition and powerful jaws suggest that it could also prey on moderately large oceanic prey.

A few of its features suggest that this is a nocturnal hunter. Its large eyes are equipped with a reflective green/yellow retina and they lack an expanded iris. This implies that they rely on sight to notice the silhouettes or bioluminescence of potential prey.

10. Alternative Names

– Japanese ragged-tooth shark

– Mizu-wani (Japanese), which literally means “water crocodile.”

– Kamohara’s sand-shark

– Water crocodile

11. Population And Conservation Status

This shark species is classified as near threatened in the IUCN Red List. Apparently, their population is being depleted by bycatch in pelagic longline fishing activities. It’s frequently caught in Japan by longline fisheries especially those fishing for tuna and by Australian swordfish fisheries. Most fishermen will discard it because of its small size and its meat and fins that are of no particular value in the Japanese market. However, its liver is very rich in squalene and thus there is some potential value in catching it.

12. Ancestry And History

For a while, this shark was shuffled between two genera Carcharias and Odontaspis under the family Odontaspididae before it was finally placed in its own genus, Pseudocarcharius.

Its morphology shows some relationship between the crocodile shark and the megamouth shark (Megachasmidae). In addition, it has close ties with the basking shark (Cetorhinidae), the thresher shark (Alopiidae), and mackerel sharks (Lamnidae). Recent analysis based on mitochondrial DNA suggest that the crocodile shark is most closely related to the sand sharks (Odontaspididae) or the megamouth shark. On the other hand, other analysis based on its dentition suggests that its closest relatives are the thresher sharks, closely followed by the mackerel sharks.

Fossil evidence from teeth identical to the dentition of the modern-day crocodile shark were found in Italy. The teesth date back to the Serravallian age of the Miocene epoch 13.6–11.6 million years ago.

13. Distribution And Habitat

The crocodile is distributed worldwide in tropical waters. In the waters of the Atlantic Ocean, it inhabits from off Brazil, to Cape Verde, Guinea-Bissau, Guinea, on to Angola, South Africa, and Saint Helena Island. Though, it has not been reported from anywhere in the northwestern Atlantic.

For the Indian Ocean, the crocodile shark is sighted from the Mozambique Channel to the Bay of Bengal. It occurs in Japan, Taiwan, the Korean Peninsula to Indonesia, Australia, and on to New Zealand. From there it inhabits waters towards the western coast of the Americas.

It’s a strong and active swimmer and it appears they migrate vertically to the water surface at night, and swim deeper into the water during the daylight hours. Usually, this movement is between the water surface and a depth of 590 meters (1940 feet).

They occur mostly far from land with very rare sightings inshore at the ocean bottom.

The crocodile gathered attention to itself in an unusual way in October 1985. Just a month earlier, AT&T had installed the first ever deep sea fiber optic cable. The cable was to link Gran Canaria and Tenerife in the Canary Islands. AT&T’s monitoring systems detected a short in power transmission and the same incident reoccurred three more times at different locations along the cable. After examining the cables, the evidence pointed to shark bites.

The damaged portions were repaired but at a very high cost. Eventually the fish in question were identified after checking the shark teeth fragments in the vicinity. The goblin shark, oceanic white tip, and the crocodile shark were responsible for the bites. But the crocodile shark bites were more prominent. The rare and little known crocodile shark left more than 50 teeth and fragments at the scene. The problem was eventually solved by protecting the fiber optic cables with a layer of steel tape and a dense polyethylene coating.

You can tell that this is one shark that really likes to exercise its teeth.

References:

1. https://en.wikipedia.org/wiki/Crocodile_shark

2. http://www.sharks.org/species/crocodile-shark

3. http://www.elasmo-research.org/education/shark_profiles/pseudocarcharias.htm

Photo Credits:

https://commons.wikimedia.org/wiki/File:Pseudocarcharias_kamoharai.jpg

 

 


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