Coulson and Poad: Biological characteristics of Psettodes erume/ from the Indian Ocean 177 
flounder (Platichthys  stellatus) (Campana, 
1984), New Zealand brill (Colistium guntheri) 
and C. nudipinnis (Stevens et al., 2005), mar- 
bled flounder (Pseudopleuronectes yokohamae) 
(Lee et al., 2009), and turbot (Scophthalmus 
maximus) (Yoneda et al., 2007). The finding of a 
maximum age of 16 years for Indian halibut 
from northwestern Australia, from use of sec- 
tioned otoliths in this study, indicates that this 
species is much longer lived than the maximum 
Females age of 3 years that has been obtained for this 
species in waters of northeastern India by using 
whole otoliths (Das and Mishra, 1990). The 
maximum age determined in our study also is 
slightly older than the age of 12.4 years that has 
been obtained for this species in the Persian 
Gulf by analyzing trends in monthly length fre- 
quencies (Gilanshahi et al., 2012). 
In other regions, Indian halibut have been 
caught as large as 640 and 705 mm TL (Hussain, 
1990; Gilanshahi et al., 2012) and, because of the 
sexually dimorphic growth of this species, are 
most likely to be females. Considering that the 
oldest female (11 years old) collected in this study 
was only 403 mm TL, it is not unreasonable to 
expect that Indian halibut may attain ages >20 
years. However, in those regions where Indian 
halibut is an important component of the com- 
mercial catch, regions such as those in the Ara- 
bian Sea, Persian Gulf, Gulf of Oman, and Bay of 
Bengal, fish ages have been determined by counts 
of growth zones in vertebrae or whole otoliths 
(Das and Mishra, 1990; Hussain, 1990; Edwards 
and Shaher, 1991). These apparently unvali- 
dated aging methods have led to estimates of a 
maximum age of only 3 years that, if employed 
in mortality estimates when developing manage- 
ment plans for this species, would grossly over- 
estimate the resilience of this species to fishing 
pressure (see the “Mortality” subsection later in 
Figure 6 this section). Therefore, we recommend that, for 
Mean monthly sea-surface temperatures (gray circles) in offshore those regions where Indian halibut account for an 
waters along the Pilbara coast off northwestern Australia during 2010— important component of the fishery, age estimates 
2015 and mean monthly day lengths (black circles) in the same region be determine from sectioned otoliths. Although 
during 2014 and 2015. Also shown are mean monthly gonadosomatic analysis of trends in monthly length—frequency 
indices for female and male Indian halibut (Psettodes erumei) greater data by Gilanshahi et al. (2012) has provided a 
than the total length of sex at maturity (i.e., 286 mm). Fish were caught 
by commercial trawlers in February 2014—December 2015 and durin eee : : ae 
ena surveys in August snle_Stvonnivon 2017 off the Pilbara ein SEs ne Wynichyerowtn 8 neetizible ioe ee 
Error bars indicate standard errors of the mean. Sample sizes are given proportion of their adult life, this method of aging 
above error bars. Black bars on the x-axis indicate summer and winter is not recommended (e.g., Morales-Nin, 1989). 
months, and open bars indicate autumn and spring months 
Temperature (°C) 
Day length (hours) 
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more realistic estimate of maximum age, for a 
Growth 
Results from comparisons of the von Bertalanffy 
considerably underestimated. Although this species is growth curves indicate that female and male Indian hali- 
not long-lived, the thickness, and therefore the opacity, but have different growth patterns, with females attaining 
of otoliths prevent annuli from being readily detected a larger size at age than males. This pattern of sexually 
when otoliths are read whole; similar results have been dimorphic growth is a common feature of many flatfishes, 
reported for other flatfish species, such as the starry including those of the Paralichthyidae and Pleuronectidae 
