372 
Fishery Bulletin 108(4) 
Table 4 
Main species that typified the catches of elasmobranchs recorded onboard trawl, gillnet, and longline vessels (shaded back- 
ground), and those that discriminate between the catches of elasmobranchs obtained by each pair of fishing methods (unshaded 
background). Plain font = targeted species; Bold font = bycatch species; * Denotes that the species is relatively more abundant 
and consistently caught by the sampling method on the top (horizontal) row than on the side (vertical) column. 
Trawl 
Gillnet 
Longline 
Trawl 
Aptychotrema vincentiana 
Heterodontus portusjacksoni 
Urolophus paucimaculatus 
Squatina australis 
Gillnet 
Carcharhinus obscurus 
Aptychotrema vincentiana* 
Carcharhinus obscurus 
Heterodontus portusjacksoni 
Heterodontus portusjacksoni 
Mustelus antarcticus 
Mustelus antarcticus 
Myliobatis australis* 
Furgaleus macki 
Furgaleus macki 
Longline 
Dasyatis brevicaudata 
Carcharhinus obscurus* 
Aptychotrema vincentiana * 
Dasyatis brevicaudata 
Dasyatis brevicaudata 
T rygon orrh in a dumerilii* 
Mustelus antarcticus 
Mustelus antarcticus 
Heterodontus portusjacksoni* 
Heterodontus portusjacksoni* 
Trygonorrhina dumerilii 
Furgaleus macki* 
Heterodontus portusjacksoni 
Table 5 
Biological characteristics of four elasmobranch species caught as bycatch by commercial trawl, gillnet, and longline fisheries 
operating off southwestern Australia. Length measurements are given as total lengths (TL) for Heterodontus portusjacksoni, 
Aptychotrema vincentiana , and Squatina australis, and as disc lengths ( DL ) for Myliobatis australis. * denotes a value extrapo- 
lated from the regression equation of the relation between DL and W. The true weight could not be recorded because the pectoral 
fins had been removed by fishermen. Sample size for each sex of each species is shown on Figure 4. 
Heterodontus 
portusjacksoni 
Aptychotrema 
vincentiana 
Squatina 
australis 
Myliobatis 
australis 
Females 
Length range (mm) 
198-1300 
201-1001 
228-1004 
118-800 
Weight range (g) 
39-12,250 
32-3634 
94-10,970 
117-37,811* 
Smallest mature (mm) 
715 
754 
825 
444 
Largest immature (mm) 
869 
895 
834 
472 
Males 
Length range (mm) 
180-815 
214-872 
246-859 
129-545 
Weight range (g) 
39-3920 
33-1886 
115-5500 
152-12,373* 
Smallest mature (mm) 
595 
642 
754 
365 
Largest immature (mm) 
654 
792 
707 
433 
The relationships between DW and DL for females 
and males of M. australis collectively are described by 
the following equations: 
DW = 1.70 DL + 8.16 (r 2 =0.997, n = 96), (5) 
DL = 0.58 DW - 3.01 (r 2 =0.998, n = 96). (6) 
From the values obtained from the above equations, 
the following relationships between the natural loga- 
rithms of W and DL, and of W and DW for both sexes 
are described as 
log e W = 2.91 log e DL - 8.92 (r 2 =0.999, n=91), (7) 
log e W = 3.19 log e DW - 12.25 (r 2 =0.999, n= 91). (8) 
After correction for bias (Beauchamp and Olson, 
1973), the respective back-transformed relationships 
became 
