Soon after tlie cage was removed, parrotf isfies and STirgeonflsh.es 

 Began grazing on tFte plants. 



Except in local areas where certain large herbivorous echinoids 

 or molluscs may be abundant, the influence of plant-eating 

 invertebrates in Lameshur Bay is probably minimal compared to 

 the influence of grazing fishes. This stands in striking contrast 

 to the situation in several cold-water regions where herbivorous 

 echinoids dramatically affect the diversity and abundance of 

 marine plants (Leighton, et^ al . , 1966; Kain and Jones, 1966; 

 Jones and Kain, 1967) . It is perhaps significant that these 

 areas have few plant-eating fishes . 



Some species of fishes in Lameshur Bay showed clear preference for 

 certain kinds of plants, including species that were not found 

 within the normal grazing range. This suggests that favored species 

 may be eaten as fast as they sprout close to the reef, and that 

 survival in the area is in part limited by the distribution of 

 herbivores. Some plants, notably species of Avrainvillea , Udotea , 

 Dictyota , and the sea grass , Syringodium filiforme , were able to 

 thrive close to the reef despite heavy grazing, although abundance 

 increased away from the reef. 



Distribution of animals in a given area is influenced by availability 

 of food, suitable physical surroundings (including appropriate shelter 

 for many species), and distribution of predators. 



Randall (1967) illustrated the influence of plants on fish 

 distribution in Lameshur Bay by comparing concentration of fish on 

 two natural reefs and an artificial reef. Although the natural reef 

 seemed to provide more favorable habitats, concentration of fishes on 

 the artificial reef was eleven times that of the natural, apparently 

 because of proximity of the artificial reef to a sea grass bed, and 

 thus a ready source of food. 



Most adult plant-eating fishes live on or close to reef areas in 

 Lameshur Bay with a few individuals occupying crevices at night 

 on scattered rock or coral heads on the open plain (Fig. 10) . 

 Most stay within 30 m off the reef, but occasionally groups of 

 surgeonf ishes and parrotfishes were seen as much as 60 m seaward on 



VI-168 



