FISHERY BULLKTIN: VOL. 86. NO. 4 



portance was the 34% decline in numbers between 

 10 January and 18 February on reef V. By mid- 

 February 1981 the estimated population on reef V 

 was below that on reef III. The mean number of 

 animals for reef V in February 1982 (401) was 71% 

 of that observed in January 1981 (563), although in 

 October, November, and December 1981 it exceeded 

 the January 1981 level. In January 1983, the number 

 of juveniles (537) was essentially the same as that 

 observed two years before (Table 4). 



Figure 5.— Densities of 3-yr-old juvenile 

 Panulirus cygnus in January on reef I at 

 Seven Mile Beach, Western Australia, for the 

 period 1970 through 1982. Mean and 95% 

 confidence limits are shown. Data for 

 1970-80 from Morgan et al. (1982). 



Table 4. — Mean total numbers of juvenile 

 Panulirus cygnus on three test reefs at Seven 

 Mile Beach, Western Australia, based on visual 

 estimates made by two observers. — = no 

 visual estimate made. 



1 



\ h 



■f 



1970 71 72 73 74 75 76 77 78 79 80 81 82 

 YEAR 



Growth 



Single Molt Increments 



Mean single molt increments of male and female 

 P. cygnus on reefs III and V, the treatment and con- 

 trol reefs, (Table 5) showed no significant difference 

 within either the 2-, 3-, or 4-yr-old age-classes (^test, 

 P > 0.05). Only four animals estimated to be ^5 years 

 of age were recaptured and these were all from reef 

 V. After pooling the molt increment data for the two 

 sexes there were no significant differences between 

 the mean single molt increments of 2-, 3-, or 4-yr- 

 old animals on reefs III and V (^test, P > 0.05). 



Table 5.— Mean molt increments in carapace length (mm) for sex age-class groups 

 of juvenile Panulirus cygnus from three test reefs at Seven Mile Beach, Western 

 Australia during January-May 1981. Data are mean BE (n). 



782 



