to a ridge of sharp relief running to the south and doglegging eastward near the 

 tip of Cabritte Horn Point. At this ridge the patch reef -sand substrate to the 

 west at 15 m depth meets rock outcrop to the east and, further shoreward, 

 boulder and rock rubble at depths of 10-12 meters. 



The den structures occupied were, variously, rock crevices (dens 9 and 14), 

 boulder or rock-shelf overhangs (dens 5 and 10), or live coral platforms with 

 caverns beneath (dens 3 and 6), all typified by having an entrance, or some 

 internal portion, restrictive to anything larger than a lobster. In addition, 

 most of the dens initially occupied had hard substrate floors, although at a 

 later time sand-floored dens were often occupied and other hard-floored dens 

 were often vacant. 



Selectivity for specific dens, as suggested by the initial concentration of 

 the Area 3 population, was also shown by the following (1 and 2 are discussed 

 in more detail later in the report) : 



1. Certain individuals, sonically monitored, returned to the original, 

 or other established den, after nocturnal movements. 



2. Lobsters displaced up to 200 m during sonic tracking studies homed to 

 the original den, another commonly frequented den, or a crevice proximal to one 

 of these. 



3. Certain individuals, observed daily, frequented the same den or one 

 of the 7 original dens, for periods of up to 7 days (e.g., lobsters 3231 and 

 3442, 5134 and 3132 in Figure 6). 



4. Certain individuals apparently left the entire study area but re- 

 appeared up to several months later in one of the 5 main dens (e.g., lobsters 

 3123, 3153, 3441, 3534, and 3145 in Figure 6). 



5. Thirty-eight percent of the new individuals first appeared in the 5 

 main dens (3, 5, 7, 9, and 14; Figure 7); that is, only 7 percent of the total 

 number of dens established by the end of the study. 



6. Even with the disrupting factor of diver presence, 42 percent of the 

 successive daily resights were at the den occupied the day previously (however, 

 some 8 percent of these may not have left the dens during the interim period) . 



7. Lobsters molested during capture (for tagging or measurement) have 

 been observed shortly thereafter to travel directly to, and enter, one of the 

 other established burrows. 



These data and observations show that a significant number of lobsters in the 

 study areas demonstrate selectivity of habitation. Not only do they apparently 

 distinguish these den sites from other crevices but demonstrate remarkable 

 familiarity with the relative location of them during spontaneous and forced 

 movements . 



VI -49 



