FISHERY BULLETIN: VOL. 78, NO. 2 



but admitted that Lesson's ferrugineus might 

 have priority. 



This shark is a shallow-water species, usually 

 seen at rest on the bottom during daylight hours. 

 It is not common in the Marshall Islands. Two 

 specimens were obtained from Enewetak, 1,400 

 and 1,487 mm TL, weighing 11.7 and 14.1 kg. The 

 flesh of neither was toxic. 



Fourmanoir (1961) stated that the principal 

 food of this shark consists of octopuses and xanthid 

 crabs. Gohar and Mazhar (1964) reported 

 cephalopods, fishes, and parts of corals 

 (Stylophora) from the stomachs of Red Sea speci- 

 mens (the corals were probably accidentally in- 

 gested). Hiatt and Strasburg (1960) found a rab- 

 bitfish, Siganus sp., in the stomach of one of three 

 specimens collected at Enewetak. 



The stomach of the smaller of the two specimens 

 taken during the present study contained a sur- 

 geonfish, Acanthurus glaucopareius, 95 mm SL. 

 Three other Enewetak specimens and one from the 

 Tuamotu Archipelago (to 1,615 mm TL, 20.9 kg) 

 had empty stomachs. 



Carcharhinidae (Requiem Sharks) 



Carcharhinus albimarginatus (Riippell) (Figure 

 2): The silvertip shark is one of three carcharhinid 

 sharks with white on the tips of its fins; the others 

 are the oceanic whitetip shark, C. maou (Lesson) 

 (C. longimanus a junior synonym), and the 

 whitetip reef shark, Triaenodon obesus (Riippell). 



The name silvertip has been adopted by Kato et al. 

 (1967) and others to avoid confusion with the other 

 two species with white-tipped fins. The white on 

 the silvertip's fins is not confined to the distal ends 

 but continues along the posterior margins. The 

 apex of the first dorsal fin is somewhat pointed 

 (broadly rounded on C. maou); the origin of this fin 

 is over the inner edge of the pectoral fin. The pec- 

 torals are about 18% TL (about 28% on C. maou). A 

 median interdorsal ridge is present. There are 

 usually 26 upper and 24 lower teeth. The pre- 

 caudal vertebrae vary from 115 to 125. 



Carcharhinus albimarginatus has not been re- 

 ported as poisonous [Halstead (1967, pi. VI, fig. 3) 

 illustrated it but misidentified the figure as 

 Triaenodon obesus], but it would seem to have the 

 potential for causing ciguatera because it preys in 

 part on reef fishes. In the Marshall Islands it was 

 usually seen on exposed outer reefs in water >30 

 m, though one individual was observed in the 

 Enewetak lagoon in water only 2 m deep. Bass et 

 al. (1973) summarized the depth distribution, not- 

 ing records to 400 m. This species has attacked 

 man. 



The flesh of four silvertips, 933-1,650 mm PCL 

 (15.0-73.5 kg), from Enewetak was nontoxic. 



Fourmanoir (1961) reported the following wide 

 variety of fishes from the stomachs of silvertips 

 from Madagascar: Promethichthys prometheus, 

 Pristipomoides typus, Seriola songoro, Coris 

 gaimard, Caesio coerulaureus , Acanthocybium 

 solandri , Euthynnus pelamis , and Neothunnus al- 



FIGURE 2.— Carcharhinus albimarginatus, 1,650 mm PCL, 2,154 mm TL, 73.5 kg, Enewetak, Marshall Islands. 



206 



