GRAZING GROUPS OF FISHES 



Observations were made on the mixed assemblages of fishes that ate 

 together. There is great temptation to regard these groups as 

 herds or flocks becaiase of the resemblance to sheep or cattle 

 grazing in a pasture. Typically, individuals of several species 

 traveled as a group, but separated by species to feed. In groups 

 consisting of single species of different sizes, members commonly 

 sorted out by size to feed. 



Examples of mixed groups that were seen include the following: 



June 30, 1130 hours. As a group, 8 parrotfishes (2 species), 

 7 surgeonfishes (3 Acanthurus coeruleus , 4 A. chirurgus ) , 

 4 spotted goatf ishes , traveled over the reef in 9 m depth. 

 They converged on a single dead coral head covered with 

 fine filamentous algae and nibbled it thoroughly for 2 or 

 3 minutes, then moved to an open sandy area. 



June 8, 1100-1130 hours. A group consisting of five parrot- 

 fishes (2 species) , 9 surgeonfishes (3 A. coeruleus , 6 A. 

 chirurgus ) , 3 queen triggerf ishes , and three spotted goatf ishes 

 moved together over the algal plain 20-25 m from the reef in 

 20 m depth. The group broke apart and reconvened several 

 times during 30 minutes of observation, with all of one species 

 usually splitting off together. When separated, the area 

 covered was approximately lOm^ ; when reunited, approximately 3m2. 

 Triggerf ishes traveled with the group but grazed as individuals. 

 Ground cover included species of Udotea , Dictyota , Avrainvillea , 

 Anadyomene , and mats of blue-green alga. 



July 9, 1730 hours. Fourteen parrotfishes (Scarus croicensis ) 

 and 1 surgeonfish (A. coeruleus ) traveled together, nibbling 

 on plants on the algal plain in 19 m depth, 20 m from the base 

 of the reef . 



July 15, 1600 hours. Six surgeonfishes (3 A. coeruleus , 3 Ao 

 bahianus ) traveled together, then grazed separately by species 

 15 m from the face of the reef on the plain in 17 m depth. 



July 16, 0700 hours. A group consisting of 9 surgeonfishes 

 (6 A. bahianus , 3 A. coeruleus ) 4 spotted goatf ishes, 2 parrot- 

 fishes ( Sparisoma aurofrenatum ) ? traveled together over the 

 reef in 16-18 m depth, then moved onto the plain and began to graze. 



July 18, 1200 hours. Ntraierous grazers were active on the algal 

 plain 35-40 m from the face of the reef in 20 m depth. One group 

 consisted of 7 parrotfishes (2 species) , 12 surgeonfishes (8 A. 

 coeruleus , 4 A. chirurgus ) , and 6 spotted goatf ishes. 



VI-161 



