Movement Patterns 



It has long been known that P. argus is nocturnally active, with the exception 

 of autumnal, mass emigrations, although few field studies have obtained infor- 

 mation as to the temporal and behavioral characteristics of the activity 

 period. Information during the TEKTITE study was obtained in the following 

 ways: 



1. Consistent and frequent diurnal monitoring (all missions) 



2. Series of diurnal-nocturnal surveys (8-50) 



3. Sonic tracking studies (2-50, 8-50, interim studies by surface 

 support) 



4. Short internal (1-2 hour) sequential den checks during the crepuscular 

 and night periods (12-50) 



From these various sources it was determined that diurnal movements are 

 extremely infrequent except when a lobster has been molested, as during a cap- 

 ture. Scattered observations during the dawn twilight suggested occasional 

 movement about the reef but virtually none afterward. Movement out of the dens 

 begins at about sunset and peaks about one to two hours later (Figure 8). Dur- 

 ing September, one lobster (of 27 observed) left a den at 1830 hours and six 

 others as early as 1900. By midnight virtually all active lobsters have left 

 the dens although not all lobsters leave every night; 2 of 27 remained inactive 

 during the nocturnal surveys made during 12-50. Upon leaving the burrow, lob- 

 sters moved various distances with some staying on the reef in the vicinity of 

 the den, others migrating onto the sand algal plain, and others moving entirely 

 out of the study area. Lobsters observed out of their dens at night and those 

 tracked sonically often traveled westward onto the sand-algal plain up to 300 m 

 from their den and returned before dawn (Clifton, et al, 1970). Nearly half 

 (487o) of the lobsters observed to leave a den returned to either the original 

 den or one of the other monitored dens. The earliest return was at about 2300 

 hours, only two hours after the lobster left the den. Those moving out of the 

 den area returned between 0400 and 0700, augmenting the occasional observation 

 of eastward traveling lobsters in the immediate predawn hours. 



9 



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HOURS OF THE DAY 



Figure 8. Periodicity of lobsters vacating and returning to their dens, 



VI-50 



