the algal plain, as were long queen triggerfishes and one or more 

 gray angelfishfis. Queen triggerfislies , at least, range further, 

 clearly shown by three individuals that were in-and-out residents 

 of cage two along transect line one, 100 m from the face of the 

 reef. 



Food is abundant well beyond the normal foraging range, including 

 some plant species that feeding trials showed to be preferred to 

 the species growing close to the reef. Presumably, predators that 

 roam the algal plain, such as barracuda, certain snappers, and 

 sharks, prey upon fishes that are exposed, away from the reef or 

 other cover. Small fishes can escape predation by hiding among the 

 plants on the algal plain, but those more than 10 to 15 cm long 

 would find cover with difficulty in this area. Small surgeonfishes, 

 parrotfishes, triggerfishes, puffers and filefishes (under 10 cm 

 long) were seen throughout the algal plain to the limit of plain 

 cover. 



Trunkf ishes , cowfishes, and boxfishes, with anatomy that 

 discourages many predators, were seen close to the reef on the 

 open algal plain, day and night. Except for Ostraciontids , all 

 plant-eating fishes observed during this study sought cover at 

 night. All grazing activity apparently takes place during daylight, 

 starting for most species just after sunup, and ending just before 

 sundown. Despite concerted efforts, it was virtually impossible 

 to find a plant-eating fish during the night except for the exposed 

 Ostraciontids, partially concealed queen triggerfishes and parrot- 

 fishes, and occasional angelf ishes and surgeonfishes, found only 

 with moderate cover. Damself ishes , gobies, and blennies remained 

 deep within crevices which they stayed near during the day. 



Distribution of herbivorous marine fishes on a worldwide basis 

 shows a remarkable concentration (both in diversity and biomass) 

 on tropical reefs, and a proportionately small number in temperate 

 and arctic seas (Hiatt and Strasburg, 1960). To a botanist, it is 

 even more remarkable to note, in parallel, that plants in tropical 

 areas, although diverse in kinds, are in general small and in- 

 conspicuous, while in cold and temperate seas, forests of giant 

 kelps and other large seaweeds are characteristic. 



VI-169 



