66 
Fishery Bulletin 107(1 ) 
- A 
J F M A M J J A S O N D 
Month 
Figure 5 
Mean monthly water temperatures ±1 standard 
error for (A) inshore and (B) offshore waters at 
Albany (gray circles) and Esperance (black circles) 
on the south coast of Western Australia and (C) 
mean monthly gonadosomatic indices ±1 SE for 
female western blue groper ( Achoerodus gouldii) 
and mean monthly percent frequencies of occur- 
rence of ovaries at stages III and IV (white) and V 
and VI (gray). Monthly sample sizes are shown on 
the figure. Closed rectangles on the x-axis refer to 
winter and summer months and the open rectangles 
to spring and autumn months. 
Total length (mm) 
B 147 135 59 27 19 11 6 4 
Age category (years) 
Figure 6 
Percent frequency of occurrence of female west- 
ern blue groper (Achoerodus gouldii) with mature 
gonads (gray histograms) in sequential (A) 50-mm 
length classes and (B) five-year age categories in 
samples obtained during the spawning period, i.e., 
from June to October. A logistic curve (solid line) 
and its 95% confidence limits (dotted lines) in (A) 
were derived from the probability that a fish at a 
given length is mature. Sample sizes are shown 
above the histograms for each 50-mm length class 
and each age category. 
The youngest female that was mature during the 
spawning period was 5 years old. The prevalence of 
mature females in sequential five-year age categories 
increased from 7% in fish of 5-9 years to 63% in fish 
of 20-24 years (Fig. 6B). Although the prevalence of 
mature females caught during the spawning period 
reached 81% in fish of 25-29 years, it did not reach 
100% in either the 30-34 age-class category or that 
comprising all older fish (Fig. 6B). 
Among the 200 A. gouldii with lengths between 100 
and 1041 mm and whose gonads were examined his- 
tologically, all 150 individuals <655 mm contained 
exclusively ovarian tissue (Fig. 7A) and were therefore 
females. All but six of the 50 individuals with lengths 
>655 mm contained exclusively either ovarian tissue 
(e.g., Fig. 7B) or testicular tissue (e.g., Fig. 7C). The go- 
nadal tissue of those six exceptions — fish whose lengths 
ranged from 758 to 850 mm — comprised testicular 
