SERFLING and FORD: ECOLOGICAL STUDIES OF PANULIRUS INTERRUPTUS 



dicates that, at least for this species, illumination 

 is not an inhibitory factor. In fact, it may serve as 

 a stimulus for settlement. 



In this regard it is important to note that per- 

 sistent stratus overcast in the southern California 

 coastal zone during the summer months results 

 from upwelled water coursing southward from 

 Point Conception. Thus, normal background 

 illumination from the moon and stars generally is 

 eliminated, although sky glow is present near 

 major coastal cities. Consequently, at our 

 sampling site the prevailing overcast and noctur- 

 nal illumination from the Scripps Institution pier 

 lights could have masked any lunar effect, result- 

 ing in what we observed, puerulus settlement in 

 traps during all moon phases. 



Duration of the Puerulus Stage 



Essentially nothing is known about the duration 

 of the puerulus stage of any spiny lobster species. 

 Sheard (1949) suggested that the puerulus of the 

 western Australian spiny lobster, P. longipes cyg- 

 nus, lasts for 2-3 wk, but offered no supporting 

 evidence. 



April was consistently the period of greatest 

 abundance for the last phyllosoma stage (stage 11) 



\ 1 Phyllosoma 



\2 Stage No. 



\3 / 



\ 



'.4 

 \ 



^. 6 



V7 



^ 9 

 \ 



ESTIMAIED DATE 



OF 

 METAMORPHOSIS 



TO PUERULUS 



■. 10 



\ 



i<- 2j mo.- 



Puerulus settlement- 



Aug Sept Oct Nov Dec Jan Feb Mar Apni May June July Aug Sept 



Figure 8.— Comparison of seasonal occurrence and dates of 

 greatest abundance of the phyllosoma and puerulus larval stages. 

 Data on the phyllosoma stages are from Johnson (1960). 



of P. interruptus, based on evidence obtained by 

 Johnson (1960) in extensive sampling during the 

 period 1949-1957, as summarized in Figures 8 and 

 9. Most of the late stage phyllosoma larvae he 



'Srfn Francisco 



Phyllosonia Larvae : 

 1 - No. Stage 10 

 1~ No. Stage 1 1 



.'20 Kn- 



(?C0 miles) 



Figure 9.-Offshore distribution of the late stage phyllosoma 

 larvae (stages 10 and 11) of Panulirus interruptus during the 

 period from 1949 to 1955, as reported by Johnson (1960). 



collected were taken at stations 160-320 km 

 (100-200 miles) offshore (Figure 9). Our data in- 

 dicate that the greatest abundance of pueruli in 

 coastal waters during 1969 was in early August, 

 approximately 3V2 mo after this peak in the abun- 

 dance of stage 11 phyllosomes. Assuming that the 

 duration of the eleventh phyllosoma stage extends 

 for a period of 1 mo, and that shoreward migration 

 is accomplished by the puerulus, rather than by the 

 last phyllosoma larval stage (see subsequent dis- 

 cussion), then this suggests that the puerulus 

 stage of P. interruptus may have an average 

 duration of approximately 2V2 mo. This timing is 

 represented diagrammatically in Figure 8. Thus, a 

 period of 2-3 mo appears to be a reasonable es- 

 timate for the average duration of the puerulus 

 stage. 



371 



