Coulson and Poad: Biological characteristics of Psettodes erume/ from the Indian Ocean 179 
Females 
10275 1 16152919135 1 
Frequency (%) 
Total length (mm) 
43 9 23182610 15 1 
° 
& 
> 
() 
[iS 
oO 
=) 
oO 
oO 
— 
LL 
OWi2z2s456 7 8 VY 
Age (years) 
Frequency (%) 
100 
75 
50 
25 
0 ' hi t i 
125 175 225 275 325 375 425 475 
Males 
6 295 12 ea 1 
125 175 225 275 325 375 
Total length (mm) 
4 10 32159 1465 5 1 
Frequency (%) 
0 128456 7 8 ® 
Age (years) 
Figure 8 
Frequencies of occurrence of female and male Indian halibut (Psettodes erumei) with mature 
gonads (gray bars) in sequential length classes (in 25-mm intervals of total length [TL]) and age 
classes. Samples were caught during the peak spawning period (September—February) off the 
Pilbara coast in northwestern Australia. The logistic curve (solid line) and its 95% confidence lim- 
its (dotted lines) for males by length class were derived from the probability that a fish at a given 
TL is mature. The numeral at the top of each bar indicates the sample size for that class. 
September (boreal mid-autumn), a period that is similar in 
terms of timing and duration to that found in this study 
for fish from northwestern Australia at ~19—20°S. In con- 
trast, in the Bay of Bengal at latitudes of 19—20°N, Indian 
halibut spawn from August (boreal late summer) through 
December (boreal early winter) (Pradhan, 1962; Das and 
Mishra, 1990), similar to the spawning time of other tele- 
osts in that region (Rao, 1983). The difference in the timing 
and duration of the spawning period of Indian halibut in 
the Bay of Bengal, compared with those of fish in similar 
latitudes off northwestern Australia and in the Arabian 
Sea may be related to the influence of the monsoons and 
freshwater input into coastal waters in the region of Bay 
of Bengal. 
During the summer monsoon season, the Bay of Bengal 
becomes highly stratified, with a surface layer of freshwater 
because weaker winds prevent vertical mixing (Prasanna 
Kumar et al., 2002; Sengupta et al., 2006). In contrast, 
coastal upwelling along the southern part of the west coast 
of India and upwelling, wind-driven mixing, and lateral 
advection in open-ocean waters (Bauer et al., 1991; Lee 
et al., 2000; Prasanna Kumar et al., 2001; Krishnakumar 
and Bhat, 2008) make the Arabian Sea more productive. 
Off northwestern Australia, where the nutrient-deficient 
Leeuwin Current is the dominant oceanographic feature 
(Cresswell and Golding, 1980; Koslow et al., 2008), rainfall 
and terrestrial input from rivers is limited (Molony et al., 
2011). Although in other regions, the increase in water 
