The coral colonies were attached to a rocky substrate with a 

 variety of algae between them. The substrate itself was pene- 

 trated by many deep holes and some of the colonies at the edge of 

 the reef grew out over the adjacent sand. Near the southern tip of 

 the reef some coral colonies had coalesced to form a bridge across an 

 east to west channel that partially divided the reef into a northern 

 and a southern part. In general appearance this patch reef did not 

 seem atypical of the many patch reefs in the area northeast of the 

 TEKTITE II habitat. 



Although our study was aimed at the residents of the observation reef, 

 it soon became apparent that the area in which these residents live 

 included more than the reef itself. Reef associated fishes occupy 

 interstices in the reef structure, the outer surface of the reef 

 complex, and the water space surrounding the reef. Many of the 

 fishes leave the reef to feed on midwater over the reef or on the 

 adjacent sand flats and these contiguous areas must be considered 

 part of the reef habitat. We estimate that 75 percent of the activi- 

 ties of resident fish species occurred within 2 meters of the reef 

 and that 95 percent occurred within 7 meters horizontally and 2 

 meters vertically (fig 2). The adjacent areas are also shared with 

 fishes from nearby reefs. 





/I 



I I 



[- 3.5m Kj^ 



8 J M- 



Fig. 2 Observation Reef as seen from the west side showing estimated 

 volumes in which 95 percent (dotted Line) and 75 percent 

 (dashed line) of the resident fishes' activities take place. 

 Rectangular areas are the approximations used in calculations 

 described in the text. 



VI-264 



