The lancetfish is a family of two types of fish known as the longnose and shortnose lancetfish. Both species are predators and can grow to more than 6 feet (2 meters) in length. Although lancetfishes are relatively common in oceans around the world, surprisingly little is known about the fish or its reproductive habits. The distinguishing feature of the fish is the high and raised dorsal fin, which is much bigger than the body of the fish. Both species also have a number of sharp teeth which are used for catching prey.
The dorsal fin runs along the majority of the back of the fish. It is made up of around 40 different rays and is often around double the size in height of the its body. Both species of lancetfish have a slim body that is thought to help it stay hidden from prey and predators.
The major difference between the two species of lancetfish is in the snout — the longnose has a larger and more pointed version. Aside from this there is little to distinguish between the two. Although there are only two species of lancetfish that are currently recognized there may be more which are yet to be discovered. The longnose lancetfish was first discovered in 1833 while the shortnose was recognized relatively recently in 1960.
Both types of lancetfish are predators and feed on other sea creatures. This can be seen not only from the large amount of teeth but also the big mouth. It is thought that lancetfish attack and catch prey using surprise rather than strength due to the fact that the muscles are not suited for long distance or particularly fast swimming. This is backed up by the slim body, which makes it easier for the fish to conceal itself.
Although both species are predators they are also prey for a number of other fish. For example, sharks and tuna are known to prey on the fish. Some species of seal are also thought to eat lancetfish. It has been found that lancetfishes mainly eat squid and other fish along with some crustaceans.
Despite the fact that the muscle of the fish is edible there is no large commercial market for its meat. This is largely due to the fact that the muscle is watery and hence not appetizing. Lancetfishes are regularly caught be fishermen but nearly always by accident when they get trapped in nets intended for other species.