258 
Age composition, growth, reproductive 
biology, and recruitment of 
King George whiting, 
Sillaginodes punctata, in coastal waters 
of southwestern Australia 
Glenn A. Hyndes 
Margaret E. Platell 
lan C. Potter 
Biological Sciences, Murdoch University 
Murdoch, Western Australia, 6 1 50, Australia 
E-mail address (for G. A. Hyndes): hyndes@central.murdoch.edu.au 
Rodney C. J. Lenanton 
Bernard Bowen Fisheries Research Institute 
Western Australian Marine Research Laboratories 
RO. Box 20, North Beach 
Western Australia, 6020, Australia 
Abstract , —The age structure, 
growth and reproductive biology have 
been determined for the recreationally 
and commercially important King 
George whiting, Sillaginodes punctata, 
off southwestern Australia. The maxi- 
mum lengths and ages, asymptotic 
lengths (LJ, and growth coefficients (K) 
were 596 mm, 14 years, 532 mm, and 
0.47, respectively, for females, and 
555 mm, 13 years, 500 mm and 0.53, 
respectively, for males. Sexual maturity 
is attained by 50% of female S. punctata 
by ca. 410 mm in length, and by the ma- 
jority of both female and male fish at 
the end of their fourth year of life. The 
monthly trends in the proportions of 
mature gonads and the prevalence of 
different oocyte stages and postovu- 
latory follicles indicated that, in south- 
western Australia, S. punctata spawns 
from June to September. Spawning is 
thus initiated when water tempera- 
tures are declining from their maxima. 
During the spawning period, many of 
the ovaries of large fish contained yolk 
vesicle and yolk granule oocytes, as well 
as hydrated oocytes or postovulatory 
follicles (or both), indicating that S. 
punctata is a multiple spawner. Fur- 
thermore, because hydrated oocytes or 
postovulatory follicles were often found 
together with large numbers of yolk 
granule oocytes, S. punctata presum- 
ably releases eggs in batches during the 
spawning period. Recruitment of S. 
punctata into sheltered nearshore wa- 
ters (<1.5 m) commences in late Sep- 
tember, three months after the onset of 
spawning, and continues until early 
November. When juvenile S. punctata 
reach ca. 1.5 years of age and ca. 250 
mm, the legal minimum length for cap- 
ture, they move out into slightly deeper 
waters (2-6 m) in marine embayments 
and estuaries. After attaining ages of 
ca. 4 years and lengths of ca. 370 mm, 
they then migrate from these waters, 
where fishing pressure is greatest, into 
regions near or around reefs at depths 
of 6-50 m, where spawning occurs. In 
contrast to S. punctata , the five other 
whiting species in southwestern Aus- 
tralian waters, which all belong to the 
genus Sillago, spawn between late spring 
and early autumn. In the case of the three 
Sillago species that undergo an offshore 
migration, this movement occurs at a 
relatively small size and young age and 
leads to their occupying open sandy 
areas. The implications of S. punctata 
habitat and biological data for fishery 
management are discussed. 
Manuscript accepted 18 July 1997. 
Fishery Bulletin 96:258-270 (1998). 
The King George whiting, Sillagi- 
nodes punctata , which is the larg- 
est of the 31 species belonging to the 
Sillaginidae, occurs along the lower 
west and southern coasts of Austra- 
lia (McKay, 1992), where it is a very 
important recreational and com- 
mercial species (see Kailola et al., 
1993). Although a number of stud- 
ies have been carried out on the bi- 
ology of S. punctata (Scott, 1954; 
Thomson, 1957a; Gilmour, 1969; 
Robertson, 1977; Caton 1 ; Cockrum 
and Jones 2 ), these have concen- 
trated mainly on fish caught in shal- 
low waters, in which mature fish 
tend not to be found. Although 
Cockrum and Jones 2 obtained S. 
punctata from deeper waters, where 
spawning presumably occurs, data 
on the pattern of gonadal develop- 
ment, which is required to deter- 
mine precisely the peak time and 
duration of spawning of this species, 
are very limited. Indeed, estimates 
of the timing and duration of spawn- 
ing of S. punctata have been derived 
predominantly from backcalcula- 
tions of daily growth increments of 
recently settled juveniles (Bruce, 
1989; Bruce and Short, 1992; Jen- 
kins and May, 1994; Fowler and 
Short, 1996). These latter studies, 
which were carried out off south- 
eastern Australia, indicate that S. 
punctata spawns between early au- 
tumn and early winter. However, S. 
punctata is recruited into nearshore 
waters far earlier off South Austra- 
lia than off southwestern Australia, 
which suggests that this species 
spawns later in the latter region (cf. 
Fowler and Short, 1996; Hyndes et 
al., 1996a). 
Although age structures and 
growth parameters have been esti- 
mated for populations of <S. punctata 
off southeastern Australia, the ages 
1 Caton, A. E. 1966. Preliminary synop- 
sis of biological data on the Australian 
(spotted or King George) whiting ( Sillagi- 
nodes punctatus) (Cuv. and Val.) 1829. 
CSIRO Technical Session, Department of 
Fisheries and Fauna Conservation Agenda 
Item 5, 43 p. 
2 Cockrum, K. S., and G. K. Jones. 
1992. The reproductive biology and fe- 
cundity of King George whiting ( Sillagi- 
nodes punctata ) in South Australian wa- 
ters, 1953-1988. South Australian Re- 
search and Development Institute Fisher- 
ies Research Paper 25, 18 p. 
