102 Commercial Shark Fishing in the Caribbean Area 



Figure 35 



Family Isuridae, Mackerel and Man-Eater Sharks. Only 5 

 gill openings, the lower end of the fifth in front of the origin of 

 the pectoral ; 2 dorsal fins and an anal fin ; the first dorsal fin 

 originates far in front of the pelvics ; caudal peduncle with a prom- 

 inent longitudinal ridge or keel on each side; the second dorsal 

 and anal fins much smaller than the first dorsal ; the upper margin 

 of the caudal not over 1/3 of the total length but its axis raised 

 steeply from the general axis of the trunk and its lower lobe more 

 than 1/2 as long as its upper. 



Genus Isnrus, Mackerel Sharks (so named from the shape of 

 their caudal fins) ; Makos. Teeth slender, awl-like, with smooth edges. 



Figure 35: Isurus oxyrhincus, Mako, Sharp-nosed Mackerel 

 Shark. 



Description: Trunk tapering both toward snout and toward 

 tail ; caudal peduncle much flattened above and below but broadly 

 expanded sidewise as a prominent sharp-edged keel on each side, 

 with a deep transverse furrow above and below close in front of 

 the origin of the caudal ; snout conical and below close in front of 

 a minute pore or slit; gill openings noticeably large, the first to the 

 fourth about as long as the snout (in front of mouth) ; teeth simi- 

 lar in the two jaws, 12 or 13 on a side, both above and below, 

 their edges perfectly smooth, the first two in each jaw the largest 

 and the most slender; flexuous in outline; the third upper tooth 

 much smaller than the second or fourth ; the teeth along the sides of the 

 jaws more triangular, as illustrated. First dorsal fin high and 

 triangular; second dorsal fin only about 1/7 to 1/8 as long as the 

 first dorsal ; caudal crescent in outline, its lower lobe about 3/4 as 

 long as the upper; anal similar to second dorsal in size and shape. 

 Pectoral noticeably long and narrow (a little less than 1/2 as 

 broad as long), with rounded tip and weakly concave distal margin. 



Color: Deep blue above in life (often appearing cobalt or ultra- 

 marine-blue in the water), but soon fading to a dirty slate-gray; 

 snow white below. 



Size: Matures at a length of about 6 feet; it grows to a maxi- 

 mum length of about 12 : feet; recorded weights are 135 lbs. at 

 about 6 feet, about 300 lbs. at 8 feet and about 1,000 lbs. at 10 feet, 

 6 inches ; largest West Indian specimen so far taken on rod and 

 reel weighed 786 lbs. 



Habits: One of the most active and swift swimming sharks, 

 famous for its habit of leaping clear of the water; a favorite with 

 sport-anglers ; often seen on sunny days with the dorsal fin and 

 the tip of the caudal fins cutting the surface of the sea. Found 

 both near land and far out at sea, preying on schools of the 

 smaller fishes and on larger prey, even swordfish. The flesh of this 

 and of other members of its family is perhaps the most palatable of 

 any sharks. 



