Longfin Mako Shark
The longfin mako shark (Isurus paucus) is among the five members of the family Lamnidae, which includes the shortfin mako, great white shark, porbeagle and salmon shark. Both in size and appearance, it is very similar to its sister species the shortfin mako, though this particular species may grow slightly longer (over 4 meters), is of slimmer build and possesses longer and broader pectoral fins. This different morphology is suggestive of a slower and less active lifestyle for the longfin mako, though it is still a very powerful and streamlined swimmer. Like the other lamnid sharks, the longfin mako possesses a pointed snout, a crescent-shaped tail with pronounced keels and an efficient heat exchange and retention physiology (rete mirabilia).
Relative to the shortfin mako, the longfin mako is an uncommon and poorly known species. Described in 1966 by Cuban marine scientist Dario Guitart Manday, it was designated the species names paucus, Latin for few, referring to the rarity of this species relative to the shortfin mako. It is believed to occupy a similar cosmopolitan distribution across tropical and warm temperate waters to that of the shortfin mako, but due to sporadic records, a low abundance and confusion with its more common sister species, the complete distribution remains unclear. It is an inhabitant of the open ocean and is generally found at depths of between 110 - 220 meters, at the epipelagic-mesopelagic boundary; it is rarely seen at depths above 90 meters. It is believed to be migratory in its tropical oceanic range, but specific movement patterns have not yet been identified.
The longfin mako, like the other lamnid sharks, is aplacental viviparous, meaning that the embryos hatch from eggs inside the uterus and are born live. Sexually mature females typically give birth to two pups at a time before which the unborn young are sustained by the non-viable eggs in the uterus (behaviour known as oophagy). This low fecundity, along with the late sexual maturity, low abundance and the increasing pressures from oceanic fisheries, place this species in particular conservation concern; the shark is currently listed as Vulnerable on IUCN’s Red List of Threatened species and on Annex I of UNCLOS, Annex I of the CMS Migratory Shark Memorandum of Understanding and Appendix II of CMS. The shark is typically taken in as bycatch in tropical pelagic longline fisheries for tuna, swordfish and shark, as well as in anchored gill-net, hook-and-line and other oceanic fisheries throughout its range. While the meat is considered of poor quality and has little commercial value, the fins are still valuable enough to command a price, and specimens caught are finned before their carcasses are discarded at sea. While much needed, there are currently few if any conservation measures in place for this species.