178 
July 
n=14 
August 
n=26 
September 
n=16 
October 
n=8 
November 
n=17 
December 
n=14 
| 
January 
n=21 
Frequency (%) 
T 
D2 
February 
n=20 
March 
n=17 
April 
n=25 
May 
[| n=20 
June 
n=11 
3 4 5-67-8 
Gonadal stage Gonadal stage 
Figure 7 
Monthly frequencies of occurrence of sequential stages in the gonadal 
development and sample sizes (7) of female and male Indian halibut (Pset- 
todes erumei) greater than the total length of that sex at maturity (ie., 
286 mm in total length) and caught by commercial trawler between Feb- 
ruary 2014 and December 2015 and during research surveys between 
August 2015 and September 2017 off the Pilbara coast in northwestern 
Australia. Stages include virgin (1), immature or resting (2), developing (3), 
maturing (4), prespawning (5), spawning (6), spent (7), and recovering (8). 
Black bars highlight values for fish with gonads at stages 5-6. 
Fishery Bulletin 119(2-3) 
Indian halibut no difference was assumed, and 
growth curves were fit to data for females and 
males combined (Fig. 4; Hussain, 1990; Edwards 
and Shaher, 1991; Gilanshahi et al., 2012). 
The results of this study indicate that the early 
growth of females and males is similarly rapid, 
with the majority of growth occurring in the first 
3-4 years of life. Although findings from previous 
growth studies indicate rapid early growth as well, 
they also indicate that growth is sustained, with 
little or no asymptote (Table 1, Fig. 5). The discrete 
length modes of individual age groups identified in 
monthly length—frequency data of fast growing, 
short-lived species enable programs, such as the 
systems of methods known as electronic length— 
frequency analysis (KLEFAN) and multiple 
length-frequency analysis (MULTIFAN), to be 
valuable alternatives for determining fish growth 
(e.g., Morales-Nin and Aldebert, 1997; Bellido 
et al., 2000; Campana, 2001). If applied to long- 
lived, slow-growing species, however, these tools 
involve the use of the well-defined length modes of 
the youngest cohorts of a species to fit a growth 
model to all fish (Campana, 2001). Species that 
have a broad spawning period are also not suitable 
for such analysis because the long spawning period 
results in age cohorts with a wide length distribu- 
tion that obscures the distinction between those 
cohorts (Morales-Nin and Ralston, 1990). 
Spawning 
Latitude, and therefore water temperature, influ- 
ences the timing and duration of the spawning 
period of fishes (e.g., Gray et al., 2012; Wakefield 
et al., 2015). The commencement of the spawn- 
ing period for Indian halibut in late winter or 
early spring is typical of temperate species (e.g., 
Hyndes and Potter, 1997; Morato et al., 2007; 
Gray and Barnes, 2015; Coulson et al., 2017), in 
which an increasing photoperiod or rising tem- 
peratures stimulate gonadal recrudescence (Lam, 
1983). However, the timing of the spawning period 
of Indian halibut through spring and summer is 
also similar to that of a range of teleost species in 
tropical and subtropical waters (e.g., Mackie, 2000; 
Sumpton and Brown, 2004; Grandcourt et al., 
2006; Russell and McDougall, 2008). 
Results from reproductive studies of Indian 
halibut in the Arabian Sea by Hussain (1990), at 
a latitude (~24-25°N) higher than that consid- 
ered in this study, indicate that the spawning 
period for Indian halibut occurred early and was 
far more restricted, from March (boreal early 
spring) through May (boreal late spring), than the 
(e.g., MacNair et al., 2001; Fischer and Thompson, 2004; spawning period observed in this study. However, Ramana- 
Pearson and McNally, 2005; Yoneda et al., 2007). Das and than and Natarajan (1979) determined that, at the far 
Mishra (1990) identified a difference in length at age of lower latitude of ~11°N in the Arabian Sea, Indian halibut 
the 2 sexes (Fig. 4), but in the other previous studies of had a more extended spawning period, from May through 
