FISHERY BULLETIN: VOL. 72, NO. 4 



Figure 34. — Area of the reef showing scrape marks made by the teeth of grazing parrotfishes, mostly Scarus sordidus. 

 Note that grazing has occurred only where dead coral is overgrown with algae — no living coral has been scraped. 



This, the smallest Hawaiian species of Scarus 

 (not exceeding a length of about 300 mm), is by far 

 the most numerous parrotfish over exposed basalt 

 on shallow reef flats and adjacent reef faces. The 

 smaller juveniles and females, usually in aggrega- 

 tions, tend to occupy the shallow flats, the larger, 

 distinctively hued males, which are usually soli- 

 tary, tend to occupy the reef faces. This species is 

 like S. sordidus in grazing during the day; how- 

 ever, whereas S. sordidus usually scrapes algae 

 from the surface of dead coral, S. taeniurus 

 ordinarily scrapes algae from the surface of rocks. 



At night S. taeniurus rests in reef crevices. Dur- 

 ing the series of night observations in which I 

 checked the incidence of mucous envelopes, all 11 

 S. taeniurus, which were less than 300 mm long, 

 were in envelopes (Figure 35). 



The two individuals ( 150 and 243 mm) that were 

 collected during midday were full of bits of algae, 

 mixed with calcareous powder, organic slurry, and 

 sand (proportions undetermined, but the algae 

 made up less than 20%), with no evident trace 

 of coral tissue or mucus. 



CONCLUSION. — Scarus taeniurus is a diurnal 

 herbivore that usually feeds by scraping benthic 

 algae from rock surfaces. 



Scarus rubroviolaceus Bleeker — tthu palukaluka 



During the day this parrotfish ranges over the 

 reef, usually in mixed groups of several males and 

 females. It occurs on all the inshore reefs, but 

 mostly on rock substrata. Generally, using the 

 sides of its jaws, it takes one bite and then with- 

 draws a few centimeters before approaching for 

 another bite. 



At night S. rubroviolaceus rests in reef crevices. 

 While surveying the incidence of mucous en- 

 velopes in resting parrotfishes (see accounts for S. 

 sordidus and S. taeniurus above), of the nine S. 

 rubroviolaceus that were observed, including both 

 males and females approximately 200 to 500 

 (mean 394) mm long, none were in envelopes (Fig- 

 ure 36). Because the large and distinctive males of 

 S. rubroviolaceus are not numerous, I came to 

 recognize some individuals. These often returned 



996 



