Longfin Mako Shark - Biology and Ecology

Biology and Ecology

The biology of the longfin mako is little-known; it is somewhat common in the western Atlantic and possibly the central Pacific, while in the eastern Atlantic it is rare and outnumbered over a thousandfold by the shortfin mako in fishery landings. The longfin mako's slender body and long, broad pectoral fins evoke the oceanic whitetip shark (Carcharhinus longimanus) and the blue shark (Prionace glauca), both slow-cruising sharks of upper oceanic waters. This morphological similarity suggests that the longfin mako is less active than the shortfin mako, one of the fastest and most energetic sharks. Like the other members of its family, this species possesses blood vessel countercurrent exchange systems called the rete mirabilia (Latin for "wonderful net", singular rete mirabile) in its trunk musculature and around its eyes and brain. This system enables other mackerel sharks to conserve metabolic heat and maintain a higher body temperature than their environment, though it is uncertain whether the longfin mako is capable of the same.

The longfin mako has large eyes and is attracted to cyalume sticks (chemical lights), implying that it is a visual hunter. Its diet consists mainly of small, schooling bony fishes and squids. In October 1972, a 3.4 m (11 ft) long female with the broken bill from a swordfish (Xiphius gladias) lodged in her abdomen was caught in the northeastern Indian Ocean; it is unknown whether the shark was preying on swordfish as the shortfin mako does, or encountered the swordfish in some other aggressive context. Adult longfin makos likely have no natural predators, while young individuals may fall prey to larger sharks.

As in other mackerel sharks, the longfin mako is aplacental viviparous and typically gives birth to two pups at a time (one inside each uterus), though a 3.3 m (11 ft) long female pregnant with eight well-developed embryos was caught in the Mona Passage near Puerto Rico in January 1983. The developing embryos are oophagous: once they deplete their supply of yolk, they sustain themselves by consuming large quantities of non-viable eggs ovulated by their mother. There is no evidence of sibling cannibalism as in the sand tiger shark (Carcharias taurus). The pups measure 97–120 cm (3.18–3.9 ft) long at birth, relatively larger than the young of the shortfin mako, and have proportionally longer heads and pectoral fins than the adults. Capture records off Florida suggest that during the winter, females swim into shallow coastal waters to give birth. Male and female sharks reach sexual maturity at lengths of about 2 m (6.6 ft) and 2.5 m (8.2 ft) respectively.