752 



Fishery Bulletin 101(4) 



10 

 8 

 6 



4 

 2 

 



10 

 8 

 6 

 4 

 2 

 



10 



g, g Peel-Harvey 



i 6  ^s'^^^y 



2 

 



10 

 8 

 6 

 4 

 2 

 



10 

 8 

 6 



4 

 2 

 



Leschenault 

 Estuary 



Koombana 

 Bay 



Cockburn 

 Sound 



Shark Bay 



iir~i-i — m 





V \, 



O -1' 



% 



'^ \ '^^'^ ^<5 \ ' 



Figure 5 



Mean monthly gonad weights +95'/f confidence intervals for female Por- 

 tunus pelagicus and the percentage of ovigerous females among all adult 

 female P. pelagicus in the five bodies of water sampled. The black rectangles 

 on the -V axis refer to summer and winter months and open rectangles to 

 autumn and spring months. 



bana Bay and Cockburn Sound peaked at 32-36% in No- 

 vember and December in Koombana Bay and at 35-45% 

 in October to December in Cockburn Sound. Although 

 the corresponding percentage contributions of ovigerous 

 female crabs were far lower in the Leschenault and Peel- 

 Harvey estuaries than in the above two embayments, they 

 still reached their maxima at the same time of the year 

 (Fig. 5). Few or no ovigerous female crabs were caught in 

 either of those estuaries or embayments between March 

 and August. Ovigerous females were found in Shark Bay 

 in each of the ten months in which that embayment was 

 sampled and, unlike the situation in the two more southern 

 marine embayments, their monthly contributions to the 

 overall number of adult female crabs did not vary markedly 

 throughout the year (Fig. 5). 



Trends exhibited by oocyte development 



The maximum diameter of the oocytes increased progres- 

 sively from 95 pm in stage-I gonads to 315 pm in stage-IV 

 gonads (data not shown). The modal oocyte diameter 

 of the distinct and largest cohort of oocytes in stage IV 

 (240-259 ^m) was only slightly less than that of the fertil- 

 ized yellow external eggs found under the abdominal flap 

 of ovigerous females (300-319 /jm). The most advanced 

 oocytes in ovaries at stages III and IV were at the early 

 and late yolk-granule stage, respectively. The presence of 

 two distinct size cohorts of oocytes in the ovaries of large 

 females with grey eggs under their abdomen (i.e. eggs that 

 had been fertilized for several days) is consistent with the 

 view that large female P. pelagicus are multiple spawners. 



