FISHERY BULLETIN: VOL. 78, NO. 2 



Scarus gibbus Riippell (Figure 46): The name 

 Scarus microrhinos Bleeker has generally been 

 used in the Pacific for this species (Schultz 1958), 

 and it is under this name that its toxicity has been 

 reported (Halstead 1967). Smith (1959) resur- 

 rected the name Scams j^t66«s Riippell for the Red 

 Sea form of this species, though he still recognized 

 S. microrhinos. Schultz (1969) placed four nomi- 

 nal species, including S. microrhinos, under the 

 one name S. gibbus. The large males are readily 

 distinguished by the near-vertical anterior profile 

 of the head. Other useful characters for distin- 

 guishing the species are four median predorsal 

 scales, three row^s of scales on the cheek, and 16 or 

 17 pectoral rays. 



Of 19 specimens, 326-414 mm SL, 1.05-2.8 kg, 

 speared from Enewetak, only 1 of 410 mm (2.3 kg) 

 was slightly toxic (mongoose reaction of 1). 



Scarus rubroviolaceus Bleeker (Figure 47): This 

 parrotfish w^as selected as the type-species of a new 

 genus, Scarops, by Schultz (1958) principally on 

 the basis of its having a single enlarged row of 

 teeth on each upper pharyngeal bone. This genus, 

 however, was not recognized by Rosenblatt and 

 Hobson (1969). The primary phase of S. rubro- 

 violaceus is reddish with small blackish spots 

 and short streaks on the scales; the terminal male 

 phase (the nominal Pseudoscarusjordani Jenkins 

 and Callyodon africanus Smith were based on this 

 form) is complexly colored, but mainly purplish on 

 the anterior part of the body and abruptly green 



posterior to about the base of the seventh dorsal 

 spine (this bicolored effect more evident in live 

 than on freshly dead specimens); the head is 

 mainly blue-green, shading to orange-yellow on 

 the opercle, with transverse bands of turquoise 

 and salmon on the lips and chin. There are gener- 

 ally 6 median predorsal scales, 3 rows of scales on 

 the cheek, and 15 pectoral rays. 



Like the other species of Scarus, S. rubro- 

 violaceus is closely tied to coral reefs. It ranges 

 from east Africa to the tropical eastern Pacific. 

 Although this species has not been reported as 

 poisonous, it would seem to have the same poten- 

 tiality of causing ciguatera as other parrotfishes 

 which may be toxic. 



Three specimens, 355-370 mm SL, 1.4-1.6 kg, 

 were obtained from Enewetak in order to test for 

 possible toxicity. None were toxic. 



Rosenblatt and Hobson ( 1969) wrote, "All of the 

 eastern Pacific species of Scarus feed by scraping 

 algae from the surface of rocks. We did not see 



evidence that they bit off pieces of coral " Scarus 



rubroviolaceus is one of the four species they 

 studied. Glynn et al. ( 1972), on the other hand, 

 included S. rubroviolaceus among the three 

 scarids they regarded as coral predators from ob- 

 servations off Panama. 



Acanthuridae (Surgeonfishes) 



Acanthurus xanthopterus Cuvier and Valen- 

 ciennes (Figure 48): This is the largest member of 



FIGURE 46.— Scarus gibbus, 417 mm SL, 2.8 kg, Tahiti, Society Islands. 



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