3. Lobsters are highly l©calized to a given area of reef for a period of 

 one to several months. Total population turnover occurred within this time 

 interval with immigration and emigration occurring continuously. Some portion 

 of the emigrants, weeks or months later, returned to the same den or general 

 area of the reef, demonstrating a homing and orientation mechanism and an appar- 

 ently learned familiarity with the region. The magnitude of emigration was 

 roughly balanced by immigration. 



4. Emigrants do not move alongshore for relatively small distances but 

 instead, are hypothesized to move offshore for some unknown distance. Likewise, 

 immigrants probably come from offshore waters. 



5. The mean carapace length of males and females remained relatively con- 

 stant throughout the study with males averaging 114 mm and females 96 mm, 



6. Lobsters smaller than 50 mm in carapace length were absent from the 

 study areas, indicating that preferred habitat changes with size or age of the 

 lobster. Total size range for the population studied was 70 to 170 mm (males) 

 and 56 to 140 mm (females). 



7. Males comprised 75% of the population in April, then declined gradually 

 to 547o in September. As population turnover progressed, males selectively 

 moved out of the study area as compared to females. 



8. The spiny lobster is highly social in behavior. Multiple habitation 

 of dens was as frequent as individual habitation during most of the study. 



9. All dens were typified by having an entrance, or some internal portion, 

 restrictive to anything larger than a lobster. Most of the commonly occupied 

 dens had hard substrate floors. 



10. Lobsters demonstrate a high degree of selectivity for a specific den 

 and readily "home" to that den or nearby den when displaced up to 200 meters, 



11. The spiny lobser is nocturnally active, leaving the den at about 

 sunset to 2 hours after sunset and returning 1 to 2 hours before sunrise. 

 Movements out of the den during daylight hours, unless forced through "harass- 

 ment," was non-existent. 



12. The mechanism for "homing" to a given area of the reef appears to be 

 non-visual since orientation occurs during periods of lowest visibility. 



13. Diver presence and "harassment", whether it be casual or directed 

 (capture and tagging), resulted in a significant alteration in the distribution 

 of the population. As the study progressed, lobsters dispersed from originally 

 frequented dens into atypical, previously empty crevices. The average number 

 of lobsters per occupied den went from 5.3 to 1.3 from April through September. 

 Tagged lobsters reacted more strongly to diver presence than untagged lobsters. 



VI-56 



