FISHERY BULLETIN; VOL. 78, NO. 2 



of these sharks were killed by powerheads when 

 their aggressive behavior and proximity war- 

 ranted. On 12 July 1975 the companion diver of 

 the author, Russell E. Miller, sustained 7 gashes in 

 his head requiring 25 stitches as the result of an 

 attack by a C. amhlyrhynchos of about 1,500 mm 

 TL. The shark first exhibited threat posturing (see 

 Johnson and Nelson 1973) at the back of the au- 

 thor. Miller sounded a warning by rapping on his 

 scuba tank with his powerhead handle. The shark 

 immediately turned and swam toward him, re- 

 peating the exaggerated sinuous swimming of its 

 threat behavior as it approached. Miller struck the 

 shark with his powerhead but the shell misfired. 

 The shark came on to slash his head (and cut the 

 rubber strap of his face mask) with its upper jaw. 

 On another occasion Gordon W. Tribble had the 

 end of his speargun seized by a gray reef shark and 

 vigorously shaken. 



Richard C. Wass ( 1971) has made a comparative 

 study of the biology of the gray reef shark and the 

 sandbar shark in the Hawaiian Islands. 



Carcharhinus galapagensis (Snodgrass and Hel- 

 ler) (Figure 4): This shark is circumtropical in 

 distribution, but as noted by Garrick (1967), it 

 shows a preference for the sea around oceanic 

 islands. 



The Galapagos shark has no distinctive mark- 

 ings; it is dark gray dorsally, pale ventrally. The 

 origin of the first dorsal fin is anterior to the inner 

 free corner of the pectoral fin. The second dorsal fin 

 is relatively large for a Carcharhinus, its height 

 2.4-2.8% TL. A distinctive median interdorsal 

 ridge is present on the back. There are 26-30 upper 



teeth (the anterior upper teeth broadly triangular) 

 and 26-29 lower teeth. The precaudal vertebrae 

 range from 103 to 109. 



A single specimen, 1,831 mm PCL, 2,426 mm 

 TL, 41.2 kg, was collected at Enewetak. Its flesh 

 was nontoxic. 



Tester'^ examined the stomach contents of 41 

 Galapagos sharks caught from the Hawaiian Is- 

 lands; 51% were empty. Sixty percent of the 

 sharks had eaten bony fishes, 35% cephalopods, 

 20% sharks and rays, and 10% crustaceans. He 

 commented that the larger individuals (maximum 

 length estimated as 10 ft or 3,048 mm) fed mostly 

 on larger fishes which were torn into chunks. He 

 regarded it as a dangerous species; Randall ( 1963) 

 documented a fatal attack. 



Bass et al. ( 1973) found food in 18 of 22 individu- 

 als of this species; 12 of the stomachs contained 

 teleost fishes (serranid, Platycephalus , and a 

 flatfish) and 10 had squids or octopuses (plus the 

 shell of a bivalve mollusk). 



The Enewetak specimen was empty as were 

 three others 1,460-1,690 mm PCL from the Pit- 

 cairn Group. One of 1,580 mm PCL from Rapa 

 contained the head of an unidentified eel. 



Carcharhinus limbatus (Valenciennes) (Figure 

 5): The shark occurs in the Atlantic as well as the 

 Indo-West Pacific. In the Atlantic it bears the 

 common name of blacktip shark, a name which is 

 poor for the species in the Pacific for two reasons. 



■'Tester, A. L. 1969. Final Report, Cooperative Shark Re- 

 search and Control Program, University of Hawaii. Mimeogr. 

 Rep., 47 + 36 append, p. 



Figure a.— Carcharhinus galapagensis, 1,831 mm PCL, 2,426 mm TL, 87 kg, Enewetak, Marshall Islands. 



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