Jones et al.: Species compositions of elasmobranchs caught by three commercial fishing methods 
367 
each individual in a large, randomly selected subsample 
were recorded. Each elasmobranch species caught by 
gillnetting and longlining was categorized as either 
targeted, byproduct, or bycatch, whereas those taken by 
trawling, where prawns and scallops are the target spe- 
cies, were categorized as either byproduct or bycatch. 
Trawling was undertaken mainly at depths of 8 to 
13 m in a marine embayment on the lower west coast 
of Western Australia and, to a lesser extent, at depths 
<32 m and at distances within 20 km from the main- 
land along that coast. The trawl net, in which the co- 
dend consisted of 45-mm mesh, was towed for 60-180 
min at a speed of ~6.5 km/h. Commercial gillnet fisher- 
men deployed up to 7000 m of either 165- or 178-mm 
stretched mesh net that was set for up to 24 hours at 
depths of 24-73 m, whereas longlines, consisting of 360 
hooks attached to approximately 6400 m of mainline, 
were set for an average of 3 hours at depths of 65-73 m. 
Multivariate analysis 
The square root of the percent contribution of the number 
of each elasmobranch species to the total catch of all 
elasmobranchs recorded in each sample during regular 
onboard observations of the catches taken by each fishing 
method was used to construct a Bray-Curtis similarity 
matrix, which was then subjected to nonmetric multidi- 
mensional scaling (nMBS). One-way analysis of simi- 
larities (ANOSIM) was used to test whether the species 
compositions of the elasmobranch catches taken by the 
three fishing methods were significantly different and, 
if so, pair-wise ANOSIM tests were used to test for dif- 
ferences between the compositions of the elasmobranchs 
obtained by each pair of methods. The R-statistic value 
was then employed to ascertain the extent of any differ- 
ences between the compositions of those catches (Clarke, 
1993). R-statistic values approaching 1 demonstrate 
that the species composition of the a priori groups dif- 
fered markedly, and a value of approximately 0 indi- 
cates that the species compositions of those groups are 
very similar. Similarity percentages (SIMPER; Clarke, 
1993) were used to identify the species that typify the 
samples obtained by each fishing method and which 
species are responsible for discriminating between the 
samples caught by each pair of methods. The ordination 
and associated tests were undertaken with the PRIMER 
vers. 6 statistical package (Clarke and Gorley, 2006). 
Length and weight measurements 
A randomly selected subset of individuals collected 
during regular onboard observations, together with 
additional randomly selected individuals provided by 
commercial fishermen, yielded a total of 516 H. portus- 
jacksoni, 340 A. vincentiana, 362 S. australis, and 218 
M. australis, which were brought to the laboratory and 
processed. The data derived from the samples were used 
to construct length-frequency histograms and to derive 
sex ratios and reproductive data for the species. The sex 
of each individual was recorded and the total length 
114°E 115°E 116°E 117°E 118°E 119°E 
Figure 1 
Map showing the region between the northernmost and east- 
ernmost limits of southwestern Australia from which elas- 
mobranchs were recorded onboard commercial trawling (dark 
gray area) and gillnetting and longlining vessels (light and 
dark gray areas). 
(TL — tip of snout to tip of tail) and total weight (W) of 
each H. portusjacksoni, A. vincentiana and S. australis 
were measured and weighed to the nearest 1 mm and 
1 g, respectively. The disc length ( DL — tip of snout to 
the junction of the tail and pelvic fins) of each M. aus- 
tralis was measured to the nearest 1 mm and the disc 
width (DW) and weight of each fully intact individual 
were recorded to the nearest 1 mm and 1 g, respectively. 
The relationships between DW and DL, DL and DW, 
and between the natural logarithms of W and DL and 
of W and DW for intact M. australis were calculated by 
using least trimmed squares (LTS) regression. A resam- 
pling test was used to demonstrate that the above data 
for the two sexes could be pooled. The above relation- 
ships were used to estimate the DW and W of the small 
number of M. australis (-15%) whose pectoral fins had 
been removed by fishermen for commercial sale. Note 
that, in the results, the sample size (n) and coefficient 
of determination (r 2 ) refer to the trimmed data for the 
individuals used for the analyses. 
Length at maturity 
The reproductive tracts of the females and males of A. 
vincentiana, S. australis, and M. australis were assigned 
to one of the following maturity stages by using the crite- 
ria outlined in White et al. (2001). For females, stage 1 = 
uteri small and thin and oocytes not macroscopically vis- 
ible; stage 2 = uteri enlarging but still thin and oocytes 
becoming visible but not yet containing yolk; stage 3 = 
uteri enlarged and oocytes yolked; stage 4 = pregnant, 
and stage 5 = uteri or cloaca distended, indicating that 
parturition had recently occurred. For males, stage 1 
= seminal vesicles small and thin and testes not well 
defined; stage 2 = seminal vesicles enlarging and start- 
ing to become coiled, but testes not yet lobed; stage 3 = 
