350 Memoir Sears Foundation for Marine Research 



widely in strength from specimen to specimen and gradually fades after preservation in 

 formalin or alcohol. The pectorals are conspicuously tipped with black; the dorsals, anal 

 and lower lobe of caudal are also black-tipped in young, but fade more or less with growth. 



Size. This Shark may mature at a length no greater than about four to five feet; 

 adults perhaps average 5^/2 to 6V2 feet, and few grow longer than seven or possibly eight 

 feet in length. It is, however, relatively much larger at birth than many other sharks. 

 Embryos 21 to 23 inches (nearly ready for birth) have been taken from females only four 

 to five feet long, and embryos 23 to 26 inches (580 to 660 mm.) from a Pacific speci- 

 men of about 6 feet 9 inches (2,070 mm.). A specimen of about 28 inches (705 mm.) 

 weighed about 4.2 pounds (1.9 kilo); one of about 47.7 inches (1,210 mm.) about 19.6 

 pounds (8.9 kilo); one of about 54.2 inches (1,375 mm.) about 32 pounds (14.5 kilo); 

 one of about 61.3 inches about 42.2 pounds (19. i kilo); and one of about 65.8 inches 

 about 68.3 pounds (31 kilo)." 



Developmental Stages. Embryos of this species have been reported repeatedly, but 

 we find no statement as to whether it is viviparous or ovoviviparous, although the large 

 size which the embryos reach before birth suggests the former; nor do the specimens we 

 have studied (see Study Material, p. 346) clarify the matter. Three to nine embryos have 

 been recorded, but the usual number is four to six, with the sexes in approximately equal 

 numbers. 



Habits. This is a very active, swift-swimming shark, often seen in schools at the 

 surface, frequently leaping clear of the water, sometimes revolving as much as three 

 times around the horizontal axis in the air before falling back into the sea.*' It is en- 

 countered indifferently near shore and out at sea. It feeds on fishes, its teeth suggesting 

 chiefly the smaller species, and probably on squid; menhaden (Brevoortia) and butterfish 

 (Poronotus triacanthus) have been found in the stomachs of North Carolina specimens, 

 and 24 California sardines (Sardinops caerulea) in an eastern Pacific example. Like sun- 

 dry other sharks, it devours sting-rays on occasion and their spines have been found 

 imbedded in its jaws. On the other hand, smallish Black-tipped Sharks have been found 

 in the stomachs of larger sharks of other species. 



Embryos in gravid females taken oflF Biloxi, Mississippi, in midsummer were small;** 

 but larger embryos nearly ready for birth were taken around southern Florida in April, 

 suggesting that the period of gestation is nearly a year, and that the young are born chiefly 

 in late spring. Other than the foregoing, nothing is recorded of its habits, notwithstanding 

 that it has been known to science for more than a century. 



Relation to Man. Such of the larger specimens as are taken in shark fisheries in 

 Florida or elsewhere are put to the same uses as other species. Thanks to the readiness 

 with which it takes a hook baited with fish (stiU or trolled) many are so caught; in fact, 

 it is often caught by anglers trolling for tarpon in Florida waters. But reports differ as to 



42. Florida specimens measured and weighed by Stewart Springer. 



43. Recent observation off Biloxi, Mississippi, by Stewart Springer. 



44. About 125 mm. J personal communication from Stewart Springer. 



