MORGAN ET AL.: STOCK AND RECRUITMENT RELATIONSHIPS IN PANULIRUS CYGNUS 



Africa by Smale (1978), and similarly Booth 

 (1979) suggested that varying survival and pos- 

 sible changes in location of juveniles may occur 

 in Jasus edwardsii (Hutton) at Castlepoint in 

 New Zealand as a result of periodic sand move- 

 ment in the area. Chittleborough (1975) has 

 pointed out that the availability of food on the 

 coastal reefs is probably the predominant factor 

 limiting the survival of juveniles. Studies in 

 progress should provide further data to examine 

 this hypothesis. The role of competitors and 

 predators also requires further examination. 



Because of the close relationship between the 

 level of puerulus settlement and subsequent 

 abundance of recruits to the fishery, the level of 

 puerulus settlement can be taken as an indicator 

 of the likely level of the future fishery. The data 

 for Seven Mile Beach, which is near the center of 

 the range of population, appears to provide a 

 satisfactory basis for this prediction up to the 

 present time. However, its use as the sole mea- 

 sure of puerulus settlement would introduce 

 assumptions regarding the future puerulus dis- 

 tribution. The densities of juveniles on small test 

 reefs do not appear at this time to provide a good 

 basis for estimation of the future recruitment to 

 the fishery. 



The combination of a stock-dependent rela- 

 tionship between breeding stock and puerulus 

 settlement and a density-dependent relationship 

 between puerulus and breeding stock will result 

 in a population which has only one stable equilib- 

 rium point of abundance (Paulik 1973), the loca- 

 tion of this point being dependent upon the fish- 

 ing mortality rate on spawning and prespawning 

 animals. If fishing effort is high the number of 

 spawning female rock lobsters will be reduced, 

 which, from Figure 2, will lead to a higher level 

 of puerulus settlement. This higher level of 

 puerulus settlement will then result in a good re- 

 cruitment of "whites" to the fishery. The possi- 

 bility of incorporating the relationships between 

 these various life history stages into a production 

 model of the fishery is therefore feasible and 

 warrants further investigation. However since 

 the results presented here are preliminary, in 

 the sense that a longer time series of data would 

 be needed to add confidence to the relationships 

 shown in Figures 2-4, such a production model 

 may at present be premature. 



ACKNOWLEDGMENTS 



Thanks to Norm Hall for computing assistance 



and to D. A. Hancock and D. H. Cushing for their 

 valuable comments on earlier drafts. 



LITERATURE CITED 



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