POST LARVAL STAGES OF AUSTRALIAN FISHES. 
143 
other species of which the spawning habit is known, e.g. Acanthopagrus australis 
and Ambassis jacks omen sis, it might be deduced that the spawning grounds are 
the same as for these species, namely close to river mouths. The eggs are 
probably pelagic. 
Planktonic postlarvae are quite transparent and have two prominent 
series of black chromatophores. One of these is a dorsal series along the bases 
of the dorsal fins extending back to the caudal peduncle. The other series is 
ventral and extends from the base of the first anal fin-spine to the caudal 
peduncle. There are a few scattered cells on the head and an internal cluster 
lining the visceral cavity. The visceral mass is also heavily pigmented with 
other colours which fade when preserved in formalin. The body is rather 
slimmer than that of the Sparidae described above and the head is likewise 
not as deep and the snout more pointed. The head length is about 4 and the 
greatest body height 6 in the total length. The eye is approximately 3 in the 
head length and still possesses a slight ventral depression which is the choroid 
fissure. 
It appears that postlarval P. sexlineatus leave the plankton when growth 
to a length of approximately 13-0 or 14-0 millimetres has been attained. They 
then begin to frequent the sheltered weedy shallows along with the fry of 
several other common estuarine species. 
As in the Sparidae there are similar adaptive changes in body pigmenta- 
tion coinciding with the adoption of a littoral habit. In P. sexlineatus this is 
a longitudinal brownish banding on a greenish ground colour. Text figs. 3B 
to 3D show this change of pigmentation on individuals possessing respective 
lengths of 13-5, 15-0 and 18-8 millimetres. The older postlarvae shown in 
text figs. 3C and 3D were both collected in June when using the seine net in 
a shallow creek at the north end of Bribie Island. The longitudinal bands 
which increase eventually to six in number are first developed more distinctly 
on the head and anterior trunk regions. The series of black cells characteristic 
of the planktonic stages persist temporarily as a secondary pigmentation but 
disappear at a length of 25-0 to 30-0 millimetres. These chromatophores are 
greatly enlarged and spider-like in form. There is a single chromatophore 
of this type at the base of each dorsal and anal fin-spine and fin-ray and others 
on the caudal peduncle and on the ventral margin of the gut region. This 
series is most noticeable in the planktonic stage shown in text fig. 3B but the 
chromatophores decrease in relative dimensions as the fish grows larger. A 
large black irregularly shaped spot located centrally at the base of the caudal 
fin is a prominent feature of all immature trumpeters. It is noticeable first 
at about 15-0 millimetres. Postlarvae of this size also have some development 
of dark pigment cells on the membranes of the dorsal and anal fins. The head 
length in juveniles of 15-0 to 19-0 millimetres has increased to about 3f or 34 
in the total length and the body height has increased similarly to approximately 
the same proportion. The first indication of the presence of scales is to be 
noticed in postlarvae 18-5 millimetres long, especially along the lateral banding 
where the margin of each scale is outlined by a tiny semi-circle of blackish 
-pigment cells. The preopercular spines are also evident in postlarval 
P. sexlineatus of this size. 
