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Fishery Bulletin 108(4) 
ern Australia. The finding that the ray D. brevicaudata 
was the most important typifying species in the long- 
line samples indicates that this bycatch species was 
consistently present in reasonable numbers in water 
depths of approximately 70 m. Although the total num- 
ber of M. antarcticus obtained by longlining was far 
greater than that of D. brevicaudata , M. antarcticus 
was occasionally taken in large numbers and, at other 
times, not caught at all, reflecting the tendency for this 
shark species to school (Lenanton et al., 1990; Last and 
Stevens, 2009). 
Length compositions, sex ratios, and habitats 
of the four selected bycatch species 
Our data indicate that the maximum lengths of the 
females of H. portusjacksoni, A. vincentiana, S. austra- 
lis, and M. australis exceed those of males by 37%, 13%, 
14%, and 31%, respectively. Moreover, for each species, 
the sex ratio did not differ significantly from parity 
among their juveniles, and the females dominated the 
length classes of the larger individuals. The resultant 
trend for the overall sex ratios for H. portusjacksoni and 
A. vincentiana to significantly favor females indicates 
that the females of at least these two species live longer 
than their males. Such a conclusion for H. portusjack- 
soni in southwestern Australian waters is consistent 
with the results of Tovar-Avila et al. (2009), who showed 
that, in southeastern Australia, the maximum age of the 
females (35 years) of this species is greater than that 
of males (28 years). Although the overall sex ratios of 
S. australis and M. australis did not differ from parity, 
those ratios were almost certainly attributable to the 
larger individuals of these two species being propor- 
tionately less well represented in the overall samples 
of those species. In the case of S. australis, the capture 
of fewer larger individuals was mainly due to this spe- 
cies not being taken by longlining fisheries in deeper, 
offshore waters, where they had been caught by gillnet- 
ting, and thus the overall samples were swamped by 
juveniles caught by trawls in their nursery areas. The 
conclusion that larger females were under-represented 
in the overall catch of M. australis is consistent with 
a tendency for the larger individuals, which would 
presumably have been predominantly females, to be 
deflected from the net. 
The difference between the maximum lengths of the 
females and males of H. portusjacksoni in southwestern 
Australian waters (37%) was far greater than the 19% 
and 10% differences recorded for two populations of 
this species in southeastern Australian (Tovar-Avila et 
al., 2007) and the 15% difference found farther north 
in eastern Australia (Powter and Gladstone, 2008). 
The trend for females to attain a larger size than that 
of males parallels that reported by Cortes (2000) for 
populations representing 164 species and 19 families 
of sharks. However, the average difference between the 
sizes of females and males reported by Cortes (2000) 
was 10% and thus smaller than the differences observed 
for particularly H. portusjacksoiii and M. australis. 
Comparisons of the length-frequency distributions for 
each of H. portusjacksoni, A. vincentiana, S. australis, 
and M. australis in samples obtained from trawling 
in inshore waters, and by gillnetting and longlining 
farther offshore, indicated that all four species use 
shallow, inshore waters as nursery areas and that sub- 
stantial numbers of the adults of S. australis and M. 
australis are also present in these inshore habitats. 
The tendency for M. australis to use inshore areas as 
nursery areas in southwestern Australia is emphasized 
by the considerable numbers of juveniles of this species 
that were caught during a study of a permanently open 
estuary on the south coast of Western Australia (Pot- 
ter and Hyndes, 1994). Furthermore, the juveniles of 
H. portusjacksoni are also abundant in inshore waters 
off eastern Australia (McLaughlin and O’Gower, 1971). 
Because several of the mature females of A. vincentiana 
caught in inshore waters contained full-term embryos, 
they would have been poised to give birth in those wa- 
ters. However, because adults of H. portusjacksoni, A. 
vincentiana, and M. australis were caught by gillnetting 
and longlining, and S. australis was caught by longlin- 
ing, some individuals of each of these species move 
offshore as they increase in size and some may even 
live permanently in offshore waters. 
Lengths at maturity and their implications 
The greater maximum length attained by females than 
by males of each of the four elasmobranch species was 
accompanied, on the basis of gonadal criteria, by a 
greater L 50 at maturity, and the differences in L 50 
ranged from 12% for S. australis and 19% for A. vin- 
centiana to as high as 28% for M. australis and 36% for 
H. portusjacksoni. The trend for the females of these 
species to mature at a larger size than that of males 
follows the overall trend exhibited by shark species 
(Cortes, 2000). 
The values derived for the L 50 at maturity for the 
males of A. vincentiana, S. australis, and M. australis 
by using full clasper calcification as the criterion for 
maturity did not differ significantly from the corre- 
sponding values derived by using gonadal maturity as 
that criterion. This result parallels that recorded for H. 
portusjacksoni by Jones et al. (2008), for Squalus maga- 
lops by Braccini et al. (2006), and for Trygonorrhina 
dumerilii by Marshall et al. (2007). Thus, to obtain data 
that can subsequently be used to derive a reasonable 
proxy for the L 50 for males at maturity, scientists can 
rapidly record the lengths of males, determine whether 
or not their claspers are calcified, and then immediately 
return them live to the sea. Furthermore, for each of 
the four species, all of the males with uncalcified clasp- 
ers and most of those with partially calcified claspers 
possessed immature (stage 1 or 2) gonads, whereas 
those with fully calcified claspers almost invariably 
contained mature (stage 3 or 4) gonads and this finding 
thus accounts for the L 50 at maturity not being signifi- 
cantly different when gonadal and clasper calcification 
criteria are used. 
