Longfin Mako

fieldmarks: Slender, spindle-shaped body, moderately long conical snout, large blade-like teeth without lateral cusplets or serrations, long gill slits, pectoral fins broad-tipped and as long or longer than head, large first dorsal fin with light free rear tip, minute, pivoting second dorsal and anal fins, strong keels on caudal peduncle, short secondary keels on caudal base, crescentic caudal fin, ventral surface of body dusky on underside of head. Snout broadly pointed. Eyes relatively large. Mouth parabolic in shape.Body slender and elongated. Lower anterior teeth slightly protruding from jaws and in line with the laterals; anterior teeth with relatively broad, nearly straight cusps with unflexed tips; cusps of first upper anterior teeth with complete cutting edges; intermediate teeth with nearly straight or slightly hooked cusps. Pectoral fins nearly straight and very broad-tipped, anterior margins about 23 to 31% of total length and equal to or greater than head length. Origin of first dorsal fin well behind the pectoral free rear tip; first dorsal-fin apex broadly rounded and hardly angular at all stages; first dorsal-fin height greater than base length at all stages (smaller in term foetuses). Vertebral total count 195 to 197. Colour: dorsolateral coloration dark slaty blue or grey-black in life, underside white but with underside of snout and jaws dark in adults and large juveniles though not in young; dark colour of head entirely covering gill septa; dark colour of flanks extending ventrally onto abdomen in adults; pelvic fin completely dark, underside white with prominent dark margin; first dorsal fin as dark as back; anal fin dark except for white free rear tip and posterior margin.

Oceanic and tropical, probably circumtropical but records sporadic and distribution sketchily known, probably often mistaken for the apparently far more commonIsurus oxyrinchus or included with records for it. Western Atlantic: Florida, Gulf Stream off eastern USA, Cuba, southern Brazil. Eastern Atlantic: Spain, Portugal, probably Mediterranean, Morocco, Western Sahara, Canary Islands, Mauritania, Guinea-Bissau, Liberia, Ghana, ?Cape Verde Islands. Western Indian Ocean: ? South Africa, Madagascar.Western Pacific: Japan, Taiwan (Province of China), Australia (Queensland and northern New SouthWales, also possibly off northern Australia). Central Pacific: Northeast of Micronesia, between Solomon and Nauru Islands, area south of Johnston and Hawaiian Islands, near Phoenix Island, and north of Hawaiian Islands. Eastern Pacific: United States (southern California).

Maximum reported 417 cm; size at birth between 97 and 120 cm; a male (Central Pacific) was adult at 245 cm; adult females (western North Atlantic) were 245 to 417 cm long.

A little-known epipelagic, tropical and warm-temperate shark, apparently common in the western Atlantic and possibly in the Central Pacific, but rare elsewhere. Said to be deep-dwelling but bathymetric data was not available. The biology of the longfin mako is poorly known. In the eastern Atlantic this species is possibly rare compared to Isurus oxyrinchus, and landings of longfin mako in Spanish fishing ports sampled by Moreno and Morón (1992) included only 51 specimens compared with 45 679 shortfin mako (0.1%). The often slimmer build and broad, long pectoral fins of this shark suggest that it is slower and less active than its better-known relative, the shortfin mako (J. Casey, pers. comm.). Its macroceanic morphology suggests similar slow cruising in the epipelagic zone as in the oceanic whitetip (Carcharhinus longimanus) and the blue shark (Prionace glauca) rather than the more active, scombroid-like swimming of I. oxyrinchus. The longfin mako is apparently endothermic, with countercurrent vascular heat exchangers for its body musculature, eyes, brain and viscera as in other lamnids (Carey, 1982), but the levels of temperature elevation it can achieve above ambient conditions have apparently not been measured. The longfin mako is ovoviviparous, with uterine cannibalism; foetuses are larger than those of I. oxyrinchus, are full-term at 92 to 120 cm, and occur as a litter of 2 to 8 young. It may approach land to give birth. Food of this shark is presumably schooling fish and pelagic cephalopods. Michael (1993) noted that one was found with a swordfish sword stuck in its abdomen, though it is not known if swordfish are an important item of this mako's diet as with the shortfin mako.

Probably taken regularly in tropical pelagic longline fisheries for tuna and swordfish as bycatch (with some marketed in Tokyo). Historically it was often taken in the Cuban longlines fishery for sharks off the north coast of Cuba and averaged about a sixth of the total weight of sharks caught there in 1971-1972. Whether it is still as common there at present is unknown. In addition to longlines, the species is taken with hooks and lines and with anchored gill nets. It is utilized fresh, frozen and dried-salted for human consumption but the meat is of lower quality than the shortfin mako and it is often finned and discarded at sea.