Coulson et at: Biological features of Achoerodus gould/i 
67 
Figure 7 
Histological sections of gonads of western blue groper (Achoerodus gouldii). (A) Ovary of 
immature female containing numerous previtellogenic oocytes and a prominent lumen (1); (B) 
ovary of mature female containing early previtellogenic oocytes (p), cortical alveolar oocytes 
(ca), yolk granule oocytes (y), migratory nucleolar oocytes (m), and hydrated oocytes (h); (C) 
mature testes with prominent lumen (1) and sperm sinuses (ss); and (D) gonad comprising 
mainly testicular tissue (t) and numerous previtellogenic oocytes (o). Scale bars = 1000 pm 
in (A) and 200 pm in (B-D). 
tissue within which previtellogenic oocytes were scat- 
tered (Fig. 7D). 
All immature ovaries, i.e., those containing only 
previtellogenic oocytes, possessed a prominent central 
lumen (Fig. 7A). This lumen was largely or fully oc- 
cluded in mature and spawning ovaries (stages V and 
VI) (Fig. 7B). A conspicuous central lumen and periph- 
erally located sperm sinuses (Fig. 7D) were present in 
all mature testes examined histologically. 
On the basis of macroscopic examination of all gonads 
removed from fish and histological examination of a 
large subsample of those gonads, all A. gouldii <655 
mm in length were females (Fig. 8A). The prevalence 
of male fish increased progressively from 3% in the 
650-699 mm length class to 80% in the 850-899 mm 
length class, and to 100% among fish >900 mm (Fig. 
8A). The TL 50 at sex change was 821 mm (Table 2). 
Among the 891 females, 866 (97%) were green and 39 
of the 44 males (89%) were blue. All fish <550 mm were 
green (Fig. 8B). The prevalence of fish with blue coloration 
increased rapidly from 8% in the 550-599 mm length 
class to 86% in the 800-849 mm length class and reached 
100% in all fish >900 mm (Fig. 8B). The confidence inter- 
vals for the TL 50 of 779 mm at color change overlapped 
those for the TL 50 of 821 mm at sex change (Table 2). 
All fish <15 years old were females (Fig. 8A). The 
prevalence of males increased from 9% in fish of 15-19 
years to 67% in those of 35-39 years and to 100% in 
those >50 years (Fig. 8A). The trend exhibited by the 
change from green to blue with increasing age broadly 
paralleled that for the change from female to male (Fig. 
8, A and B). However, a few fish changed color at an 
even earlier age than the youngest age at which sex 
change was first found to occur. 
