Jones et al.: Species compositions of elasmobranchs caught by three commercial fishing methods 
373 
B Gillnet 
0 200 400 600 800 1000 1200 1400 
Length (mm) 
Figure 3 
Length-frequency distributions for all males and females of 
Heterodontus portusjacksoni, Aptychotrema viticentiana, Squatina 
australis, and Myliobatis australis obtained from the commercial 
catches of (A) trawl, (B) gillnet, and (C) longline vessels. Length 
refers to total length ( TL ), except in the case of M. australis 
where it refers to disc length (DL). 
W = 0.0001344 DL 2 91 , (9) 
W = 0.000004787 DW 3 19 (10) 
The M. australis caught by using the three 
sampling methods ranged from 118 to 800 
mm DL (Fig. 4, Table 5), which corresponds 
to 198-1192 mm DW. The minimum DW is at 
the extreme lower end of the range reported for 
this species at birth, and the maximum DW is 
appreciably less than the maximum DW of 1600 
mm recorded for M. australis (Last and Stevens, 
2009). The largest female caught was 800 mm 
DL and 37,811 g W, which greatly exceeded the 
545 mm DL and 12,373 g W of the largest male 
(Table 5). Both sexes were represented in each 
DL class between 100 and 549 mm, and females 
were also present in each subsequent size class 
up to 800-849 mm (Fig. 4). The length-fre- 
quency distributions for both sexes contained a 
single prominent modal length class at 150-199 
mm. The ratio of 1 female:1.27 males of M. 
australis among the individuals caught by all 
methods collectively did not differ significantly 
from parity (^ 2 =3.10, P>0.05), and the same 
was true for juveniles, i.e., 1 female:1.04 males 
(^ 2 =0.06, P>0.05). 
Lengths of females and males at maturity 
The smallest female and male of H. portusjack- 
soni with mature gonads measured 715 and 595 
mm TL, respectively (Table 5). Using gonadal 
stage as the index, we found that the TL 50 for 
female H. portusjacksoni at maturity was 805 
mm, and the TL 50 for males was 593 mm, which 
represent 62% and 73% of their respective maxi- 
mum TL. The TL 50 for males was only 12 mm 
greater and not significantly different from the 
581 mm derived by using full clasper calcifica- 
tion as the index of maturity (Table 6, see also 
Jones et al., 2008). 
The smallest female and male of A. vin- 
centiana with mature gonads were 754 and 
642 mm, respectively, and all females >896 
mm and males >793 mm were mature (Fig. 5, 
Table 5). The TL 50 for females of 798 mm at 
maturity differed significantly (P<0.001) from 
the corresponding TL 50 for males of 671 mm 
when using gonadal stage as the criterion for maturity 
(Table 6). The latter TL g0 for males did not differ sig- 
nificantly from the TL 50 of 654 mm derived by using 
full clasper calcification as the criterion for maturity 
(P> 0.05) (Fig. 5, Table 6). The TL 50 for female and 
male A. vincentiana at maturity, using gonadal status 
as the criterion for maturity, were 80% and 77% of 
their respective maximum TL. 
On the basis of gonadal data, the TL of the smallest 
mature female and male S. australis were 825 and 754 
mm, respectively, and all females >840 mm and all 
males >754 mm were mature (Fig. 5, Table 5). The TL 50 
for females (823 mm) and males of S. australis (734 
mm), derived by employing gonadal stage as the crite- 
rion for maturity, were significantly different (PcO.001; 
Table 6). The latter TL 50 was not significantly different 
(P> 0.05) from the TL 50 of 721 mm derived for male S. 
australis when using clasper calcification as the crite- 
rion for maturity (Fig. 5, Table 6). The TL 50 calculated 
for females and males of S. australis, with gonadal 
stage as the criterion for maturity, were 82% and 85% 
of their respective maximum TL. 
