812 



Fishery Bulletin 91(4), 1993 



15 



n=H02 



T'T' I ' I ' I ' I ' I 



r>=4B2 



''i m i i i i' T ^Tf'i iT 1 ' 



I I I I I I 



20 30 40 SO 60 70 80 80 100 110 120 110 140 150 ISO 

 Carapace length (mm 1 



IH Females I I Males 



Figure 2 



Size-frequency distribution of male and female Panulirus argus caught (A) 

 beneath casitas within Bahia de la Ascension (modified from Lozano et al. 

 1991a l, and (B) in traps on the continental shelf outside the bay. 



Discussion 



The occurrence of a reproductive segment 

 of the population of Panulirus argus on the 

 shelf outside Bahia de la Ascension has been 

 documented in this study. The large sizes of 

 lobsters and the evidence of mating and 

 spawning activity on the continental shelf 

 indicate that reproduction takes place in this 

 deeper, unfished habitat, as opposed to the 

 smaller sized, non-reproductive segment of 

 the population within the bay. 



Munro (1974) suggested that in coralline 

 areas it is unlikely that the amount of shel- 

 ter would be a limiting factor for spiny lob- 

 sters, but that this might be important in 

 shelf areas with sparse coral cover. The deep 

 and complex reef formations on the shelf 

 outside Bahia de la Ascension (Jordan- 

 Dahlgren et al., in press) likely offer abun- 

 dant natural shelters for P. argus. Lobsters 

 are attracted to traps for refuge rather than 

 for food (Heatwole et al., 1988), and traps 

 apparently fail to adequately sample resi- 

 dent individuals (Herrnkind, 1980). Thus, 

 the poor catches obtained during our sum- 

 mer fishings probably reflected the occupa- 

 tion of the available natural shelters by resi- 

 dent adult lobsters. The resident nature of 

 these lobsters seems to be further supported 

 by the large proportion of reproductive fe- 

 males and the high incidence of lobsters 

 with fouled carapaces. The existence of resi- 



