Acanthuras bahianus (Castelnau) . Ocean Surgeonf ish 



Ocean surgeonf ishes were frequently seen traveling over the reef, 

 occasionally stopping to graze on filamentous algae, but they were 

 most conspicuous and abundant on the algal plain, often in company 

 with other surgeonfishes or mixed species of parrotfishes and spotted 

 goatf ishes . Adults were seen actively grazing on the plain as early 

 as 0600 hours, and as late as 1830 hours, but none were found at 

 night. Longley and Hildebrand (1941) suggest that the species is 

 basically a bottom fish, with distribution correlated with the 

 occurrence of the plants upon which they feed. In Lameshur Bay, 

 adult ocean surgeonfishes were usually less than 35 m away from 

 the reef, but one adult was observed at 0800 hours 60 m from the 

 reef, and several juveniles (approximately 9 cm long) were seen 

 at the most distant experimental cage along transect II, 180 m 

 seaward. 



During feeding trials, A. bahianus sampled Lobophora , Laurencia, 

 Halimeda , Udotea , Codium , and Syringodium. Randall (1967) examined 

 23 specimens and found 91.8% of the food present was algae including 

 13 filamentous, 5 leafy, 5 fleshy, and 3 calcareous species, plus 

 diatoms, as well as 3 species of sea grasses, Syringodium filiforme , 

 Halophila baillonis , and Thalassia testudinum , which comprised 8.2% 

 of the total. About half of the stomach contents consisted of fine 

 shell and sand. 



Acanthurus chirurgus (Bloch) . Doctorfish 



Adults and juveniles of this species were occasionally seen in reef 

 areas, but were most evident during the day on the algal plain as 

 much as 35 m from the reef. One juvenile ca. 10 cm long was 

 repeatedly observed associated with an isolated rock lump populated 

 with bicolor damself ishes . The surgeonfish was seen emerging from 

 a crevice in the rock at 0535 to 0540 hours on three occasions, just 

 at first light. During the day, the fish (or one of that size) often 

 was seen near the rock, nibbling algae, sometimes in company with a 

 juvenile parrot fish) . 



During feeding trails, A. chirurgus fed upon Halimeda , Udotea , 

 Lobophora , Acanthophora , and the sea grass, Syringodium . On the algal 

 plain, they were often seen in company with other surgeonfishes, one 

 or more species of parrotfishes and spotted goatf ishes, grazing on 

 assorted algae, particularly Udotea , Dictyota , and Lobophora . 



Randall (1967) examined 20 specimens and found food in the stomachs 

 to contain 93.9% algae and organic detritus, including 9 filamentous, 

 3 calcareous, 4 leafy, 2 fleshy species, plus diatoms, and 5.7% sea 

 grasses, Syringodium and Thalassia . Sand and other inorganic matter 



VI-154 



