You have probably seen a crocodile and heard of many different types of sharks. So when you think of a crocodile shark, you might picture an animal that looks something between a crocodile and a shark. However, the crocodile shark does not look like a crocodile, but it is actually a rare known species of shark that inhabits the open ocean. The crocodile shark, otherwise known as Pseudocarcharias kamoharai, is the one of the world's smallest living shark that can reach about three feet to 3.6 feet in length. They can weigh nine to thirteen pounds, which is about the same amount as a three- month old human baby would weigh. It has a spindle- shaped body with a moderately long, bulbously cone shaped snout and a short head. All of its fins are relatively small, with an asymmetrical caudal fin. Its gill slits are very long, and it has an angular mouth. The crocodile shark's coloration is a dark brown color, and a paler brown- white color below on its belly, with sometimes a few dark blotches and a white blotch at the corner of its mouth between the first gill slit. Its fins are brown with slim translucent or white stripes on them.

 

Some of the crocodile shark's adaptations are being a lighter color on the bottom and darker on the top. For example, if a fish swimming below the shark looks up and sees the white belly, then it'll think that it's looking at the surface of the water because the shark's belly is the same color as the surface of the water. But if a bird is flying above the crocodile shark and looks down, then it'll think it's looking into deep water because the shark's back and head blends in with the deep water. Because of its size and color, you can identify it easily, but what makes it stand out is its unusually huge eyes. Its eyes are about the size of a tennis ball, and lives in deep waters; it's a nocturnal hunter, relying on its sight to seek out its prey. The crocodile shark's range is usually in deep waters, which is about 1,940 ft in depth, but it occasionally appears inshore on the bottom. It can be rare to locally abundant in the open ocean offshore and its range is oceanic to coastal; it also is circumtropical in distribution. However, there have been no sightings or reports of the crocodile shark in the western Atlantic Ocean. Sometimes it is caught by Japanese fishermen in the Pacific Ocean. The crocodile shark does very well in its oceanic environment, despite the fact that it is sometimes caught in fishing nets off the coast of Japan. Although the crocodile shark is not endangered, it is not very abundant either. The crocodile shark is at the lower risk, or near threatened status according to the IUCN (International Union for Conservation of Nature) Red List. The crocodile shark was declared endangered by the IUCN Red List in the year 2000. Unfortunately, there is currently no information on its population size, but humans hunt crocodile sharks for their liver because it has medicinal purposes. Crocodile sharks have a liver rich in oil, squalene, and low- density lipids that can comprise up to about 20% of its total weight. Crocodile shark's liver is valuable to humans because of these chemicals in its liver.

 

Shrimp, bristlemouths, lanternfishes, small bony fish, tiny shrimp and moderately large, active oceanic prey are what makes up the crocodile shark's diet. Crocodile sharks are nocturnal hunters, which means that they stay in the depths of the ocean during the day and come to the surface to hunt for its prey during the night. The crocodile shark's jaws are protrusible with non-cutting teeth; but it has powerful jaw muscles and strong jaws, which allows it to bite into its food easily. Crocodile sharks compete with other deep- sea nocturnal sharks for food. Being a predator, the crocodile shark is near the top of the food chain. There is very little known information on the crocodile shark's feeding habits. There are no known predators of crocodile sharks. Crocodile sharks snap vigorously at anything when removed from the water, and when crocodile sharks are accidentally caught in fishing nets by Japanese fishermen (or any other fisherman), they might bite the catcher who underestimates its bite. However, when it is caught, it is usually discarded because of its poor meat quality and its useless skin. The only thing that is kept is its liver. Some interesting facts that I learned are that the crocodile shark got its name from the Japanese name "mizuwani" which means water crocodile. I learned that the crocodile shark is ovoviviparous, which means that the female lays the eggs, but they stay inside of the female's body until they're ready to hatch. When they've hatched the shark pups come out and it looks like a live birth. The shark pups look exactly like the adult, only smaller, like miniature versions of them. Also, many things are unknown about the crocodile shark, such as its feeding habits and life span. There is little available data on its home range. The crocodile shark is also the only member of its species in its family. So if you ever get to see a crocodile shark in the wild or even in an aquarium, remember that you are seeing a small but rare shark that is very unique.

 

Author: Kari M.

Published: 02/2009

 

Sources: "Crocodile shark -." Wikipedia, the free encyclopedia. 31 Jan. 2009 http://en.wikipedia.org/wiki/Crocodile_shark "IUCN 2008 Red List - Pseudocarcharias kamoharai." IUCN 2008 Red List - Home Page. 1963. 31 Jan. 2009 http://www.iucnredlist.org/details/39337 Martin, R. A., and Neil Hammerschlag. "Pseudocarchariidae: Crocodile Shark." ReefQuest Centre for Shark Research Home. 2001. 31 Jan. 2009 http://www.elasmo-research.org/education/shark_profiles/pseudocarchariidae.htm "ADW: Pseudocarcharias kamoharai: Information." Animal Diversity Web. 10 Feb. 2009 http://animaldiversity.ummz.umich.edu/site/accounts/information/Pseudocarcharias_kamoharai.html Wilson, Don E., ed. Animal : The Definitive Visual Guide to the World's Wildlife. Grand Rapids: Dorling Kindersley, Incorporated, 2005. page number: 472

 

Photo Credit: http://upload.wikimedia.org/wikipedia/commons/2/23/Lamn70.jpg