Kitefin Shark - Biology and Ecology

Biology and Ecology

The lower teeth of the kitefin shark form a continuous cutting edge, enabling it to take bites out of larger animals.

Relatively common where it occurs, kitefin sharks are usually solitary in nature but may form small groups. It is a slow swimmer with a large liver filled with squalene, a lipid less dense than water, allowing it to maintain neutral buoyancy and hover above the bottom with little effort. Studies off the coast of North Africa and in the Gulf of Genoa have found males outnumbering females by 2:1 and 5:1 respectively; this imbalanced sex ratio has not been observed off South Africa and may reflect sampling bias. The kitefin shark is preyed upon by larger fishes and sharks, as well as by sperm whales (Physeter macrocephalus). Parasite data on this species is limited; an examination of two sharks caught off Ireland found three nematodes in the stomach lumen. One could be identified as Anisakis simplex L₃, while another may have been a larval Raphidascaris.

A powerful and versatile deepwater predator, the short, robust jaws of the kitefin shark give it an enormously strong bite. It feeds mainly on bony fishes (including deepwater smelts, viperfishes, scaly dragonfishes, barracudinas, greeneyes, lanternfishes, bristlemouths, cod and other gadids, grenadiers, deepwater scorpionfishes, bonito, snake mackerels, deepwater cardinalfishes, and sea toads), but also takes a wide variety of other animals, including skates, smaller sharks (Galeus, Squalus, Etmopterus and Centrophorus), squid and octopus, crustaceans (amphipods, isopods, shrimp and lobsters), polychaete worms, and siphonophores. Like the related cookiecutter shark, the kitefin shark is also capable of excising chunks of flesh from animals larger than itself, including other sharks and whales. The presence of fast-swimming fishes in its diet suggests the kitefin shark may scavenge, or have some other means of capturing faster prey. In the Mediterranean, bony fishes are the most important food year-round, with the second-most important prey being sharks in the winter and spring, crustaceans in the summer, and cephalopods in the fall. Captured males are more likely to have full stomachs than females for unknown reasons.

Reproduction in the kitefin shark is aplacental viviparous, with the embryos hatching inside the uterus and being sustained to term by yolk. Adult females have two functional ovaries and two functional uteruses; the uterus is not divided into compartments. In the Mediterranean, breeding occurs throughout the year with peaks in spring and fall; females may have a year of rest in between pregnancies. The litter size is 10–16, increasing with female size. The young are born at a length of 30–45 cm (12–18 in), varying by geographic location, after a possible gestation period of two years. The males mature sexually at a length of 77–121 cm (2.53–3.97 ft), and the females at a length of 117–159 cm (3.84–5.22 ft). There is no relationship between an individual's size at birth, size at maturity, and maximum size.