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Fishery Bulletin 108(4) 
The DL of the smallest females and males of M. aus- 
tralis with mature gonads were 444 and 365 mm, re- 
spectively, and all females and males with DL >513 
and 433 mm, respectively, were mature (Fig. 5, Table 
5). The DL 50 of 511mm (DW 50 = 879 mm) for females at 
maturity differed significantly (P<0.001) from the 399 
mm (Z)W 50 = 689 mm) of males when gonadal status was 
used as the criterion for maturity (Table 6). The latter 
DL 50 did not differ significantly (P>0.05) from the 388 
mm (DW 50 = 670 mm) derived for males at maturity 
with clasper calcification as the criterion for maturity 
(Table 6). On the basis of gonadal criteria, the DL 50 for 
females and males of M. australis at maturity were 64% 
and 73% of their DL max , respectively. 
40 r 
B Aptychotrema vinceritiana 
D Myliobatis australis 
females n=203 
males a=137 
females n=96 
males n=122 
i . i 
0 200 400 600 800 1000 1200 1400 
Length (mm) 
Figure 4 
Length-frequency distributions for females (white histograms) 
and males (black histograms) of (A) Heterodontus portusjacksoni, 
(B) Aptychotrema vinceritiana, (C) Squatina australis , and (D) 
Myliobatis australis obtained collectively by all three fishing 
methods. Length refers to total length ( TL ), except in the case 
of M. australis where it refers to disc length (DL). 
Percentage of females and males caught 
by each fishing method 
The percentage of females of H. portusjacksoni, A. 
vincentiana, S. australis and M. australis caught 
in trawls with lengths below the L 50 (TL 5 0 or 
DL 50 ) at maturity were very high and similar to 
those of males (Table 7). The percentage in trawl 
samples of both sexes with lengths less than their 
L 50 at maturity ranged from 63% for A. vincen- 
tiana, to 90% for both M. australis and S. aus- 
tralis, respectively, to 97% for H. portusjacksoni 
(Table 7). In the case of gillnet samples for three 
of the four species, the percentage of females with 
lengths less than their L 50 at maturity exceeded 
those of males and particularly so for M. australis, 
for which the values were 86% and 40%, respec- 
tively (Table 7). In longline samples, the percent- 
age of males of H. portusjacksoni with lengths 
below their L 50 at maturity slightly exceeded the 
corresponding value for females (37% and 32%, 
respectively). 
Discussion 
This study is the first to quantify the contribu- 
tion of each elasmobranch species to the total 
elasmobranch catch obtained by co-occurring 
trawl, gillnet, and longline fisheries, and to cal- 
culate the contributions made by the bycatch 
and byproduct species to the catches taken by 
each fishing method. In addition, our results 
indicate that nMDS ordination and associated 
tests would be invaluable for detecting whether 
the species composition of elasmobranchs in the 
catch produced by each fishing method changes 
in the future in response to either variations in 
fishing activity or environmental factors and, 
if so, also for elucidating the magnitude of that 
effect. This study has also produced, for four 
abundant bycatch species, the sound quantitative 
biological data of the types required by manag- 
ers for developing plans for conserving stocks 
and which are deficient for the vast majority 
of bycatch species (Stobutzki et al., 2002). The 
sizes at maturity that were determined for the 
four bycatch species in this study enabled the 
proportion of each species, which was caught by 
each fishing method before it had the potential 
to reproduce, to be estimated. 
