658 
Fishery Bulletin 96(4), 1 998 
160 
140 
a. 120 
100 
80 
o 
o® ° o o 
. o % ei 
7.75 7.85 7.95 8.05 8.15 8.25 
Na 
3.6 
3.2 
2.8 
2.4-1 
2.0 
■ ■■ ■ 
■*fV" 
o a 
7.75 7.85 7.95 8.05 8.15 8.25 
Na 
3.2 
590 
2.5- 
■ 
O." ■ 480 
4 
O 
O 
0 
8 
o 
1.8 
cm" 
°°o . * 370 1 
D °°°o° * 
260 
O o A 
00 :°* °mV 
o ° ° i £ * 
1.1 
8*°„f^ ■ 
□ A 
■ 
A A I# 
■ 
0.4 
t , ° ° ■ ‘ , , 150- 
A 
7.75 7.85 7.95 8.05 8.15 8.25 
Na 
7.75 7.85 7.95 8.05 8.15 8.25 
Na 
Figure 3 
Scatterplots of significant elemental ratios showing grouping patterns of area and age school mack- 
erel samples. Open circle = Bowen 2-year-old fish; open square = Moreton Bay 2-year-old fish; solid 
square = Rockhampton 1-year-old fish; and solid triangle = Rockhampton 2-year-old fish. Mg and 
Na are log t ,-transformed concentrations. 
in the otolith chemical composition among samples 
from the different areas (Fig. 3). The ratio of Na to P 
concentrations provided the best discrimination 
among areas, with Bowen samples distinguishable 
from Rockhampton and Moreton Bay, and samples 
from Rockhampton and Moreton Bay once again over- 
lapping in their elemental composition (Fig. 3). 
Principal component analysis provided further 
support for the strength of these proposed grouping 
patterns (Fig. 4). Bowen samples were distinguished 
from those from the other areas mainly on the first 
principal component (PC I) where most of the varia- 
tion was explained by differences in P concentration, 
whereas Na and Mg contributed most to the varia- 
tion in the second principal component (PC II). These 
two components described almost 57% of the total 
variation in the data. Rockhampton and Moreton Bay 
samples showed a similar distribution of PC scores, 
in contrast to samples from Rockhampton that 
showed some degree of separation between 1- and 2- 
year-old fish. AN OVA supported these patterns with 
significant differences detected for both the PC I 
(F=24.89, df=3, 80, PcO.0001) and PC II scores 
(F=6.30, df=3, 80, P<0.0007) among the samples. than those from Rockhampton and Moreton Bay, and 
Bowen samples had significantly higher PC I scores no differences were found between 2-year-old fish 
-0.5 0.5 
PC I score 
Figure 4 
Principal component (PC) analysis of school mackerel 
otolith elemental concentrations indicating grouping 
patterns. Open circle = Bowen 2-year-old fish; open 
square = Moreton Bay 2-year-old fish; solid square = 
Rockhampton 1-year-old fish; and solid triangle = 
Rockhampton 2-year-old fish. 
