September 30, 2010 : Tigerfish

Tigerfish 

Tigerfish is the common name for a variety of species from several different families of fish, usually on account of their colouration or otherwise fearsome appearance.

Several species in the genus Hydrocynus of the family Alestiidae are called "tigerfish" and are particularly prized as gamefish. These African fish are found in many rivers and lakes on the continent and are fierce predators with distinctive protruding teeth.

The two most common species are probably most recognizable in Southern Africa. The first is the Goliath Tiger (Hydrocynus goliath), which is found in the Congo River system, the largest of the family. The second-largest, and the southernmost species, is the Tigerfish (Hydrocynus vittatus), commonly found in the Zambezi River and in the two biggest lakes along the Zambezi, Lake Kariba in Zambia, Zimbabwe, and Cabora Bassa in Mozambique and Jozini dam in South Africa.

The name "tigerfish" has occasionally been used for species of cichlid in the genus Rhamphochromis. These are large, silver-colored fishes that may have one or two black horizontal lines running the length of the body. These fish are native to Lake Malawi in Africa. They can measure up to 2 meters (6 ft. 7 in.) in length and weigh up to 50 kg (105 lbs.) They also have very sharp teeth that can rip through skin easily; however, they are not known to eat humans.

Tigerfish can be considered Africa's equivalent of the South American piranha, though they belong to a completely different family, as they are famous for their ferocity when hunting. They have razor-sharp teeth that are interlocking, along with streamlined, muscular bodies built for speed. Tigerfish are aggressive predators. A tigerfish has a gas-filled sac in its body that it uses as a sound receiver. This transmits vibrations from the water, enabling it to detect any animals nearby and respond accordingly. A school of juveniles can tackle animals of almost any size, including any land animals that stray too close to the water's edge. Adults tend to travel in smaller groups of four or five, but they are no less dangerous. Even an individual can take down prey as large as itself. When food is scarce or the competition for food is too great, tigerfish may resort to cannibalism. This is particularly common in the dry season. Tigerfish have also been known to attack humans, these attacks can be devastating owing to their sharp teeth and aggressive hunting tactics.