412 
Fishery Bulletin 109(4) 
Table 6 
General linear model (GLM) for year and age effect in region 3 (Monterey) Pacific sardine ( Sardinops sagax) otoliths for each 
perimeter-weight profile (PWP) factor: perimeter based on area, perimeter based on length, and weight based on length. Signifi- 
cance: *= P<0.05, **=P<0.005, ***=P<0.001. 
Coefficient 
estimate 
Standard 
error 
2 -value 
P 
Significance 
Perimeter based on area 
(Intercept) 
-0.0757 
0.1471 
-0.515 
0.6069 
Year 
-0.4729 
0.2869 
-1.648 
0.0994 
Age 
-0.8406 
0.2086 
-4.029 
5.60xl0- 5 
*** 
Year:age 
-0.0045 
0.3501 
-0.013 
0.9898 
Perimeter based on area after excluding interaction term 
(Intercept) 
-0.0749 
0.1335 
-0.561 
0.575 
Year 
-0.4759 
0.1644 
-2.894 
3.80 x 10- 3 
** 
Age 
-0.8422 
0.1676 
-5.026 
5.01 x IQ 7 
*** 
Perimeter based on length 
(Intercept) 
-0.3606 
0.1494 
-2.413 
0.0158 
* 
Year 
-0.1880 
0.2881 
-0.652 
0.5142 
Age 
-0.6909 
0.2135 
-3.236 
1.21xl0 -3 
** 
Year:age 
-0.0823 
0.3520 
-0.234 
0.8152 
Perimeter based on length after excluding interaction term 
(Intercept) 
-0.3458 
0.1352 
-2.557 
0.0106 
* 
Year 
-0.2431 
0.1658 
-1.467 
0.1424 
Age 
-0.7212 
0.1701 
-4.239 
2.24xl0- 5 
*** 
Weight based on length 
(Intercept) 
0.9391 
0.1636 
5.742 
9.36xl0 -9 
*** 
Year 
-0.2670 
0.2995 
-0.892 
0.3726 
Age 
-0.7601 
0.2115 
-3.593 
3.27xl0“ 4 
*** 
Year:age 
0.7549 
0.3475 
2.173 
0.0298 
* 
Weight based on length, 2006 
(Intercept) 
0.9391 
0.1636 
5.742 
9.36xl0- 9 
*** 
Age 
-0.7601 
0.2115 
-3.593 
3.27xl0- 4 
*** 
Weight based on length, 2007 
(Intercept) 
0.6721 
0.2509 
2.679 
7.39xl0- 3 
** 
Age 
-0.0051 
0.2757 
-0.019 
0.9851 
and 7 otoliths and the mixed characteristics of region 
4 and 5 otoliths were described by Felix-Uraga et al. 
(2005) in their study of Baja California populations. The 
results from our study support the generally accepted 
belief that southern Baja California sardine represent 
a distinct stock. 
The PWP method clearly differentiated region 3 and 
4 (Monterey and San Diego) cohorts collected in 2006- 
07. The mixed results of the Port Hueneme samples 
compared with Monterey and San Diego sardine could 
indicate that Port Hueneme is a zone of overlap where 
representatives are carried south by the cool California 
Current and others are transported north by the warm 
Southern California Countercurrent. 
The PWP method has limitations for assigning fish 
to stocks or environments. Similar PWPs between re- 
gion 2 and 4 age-1 sardine, but not region 3 fish, do 
not necessarily indicate a common stock, although it is 
generally believed adult sardine in California migrate 
north during the summer (Smith, 2005; Lo et al., 2010). 
Likewise, dissimilar perimeter profiles between age-0 
and age-1 sardine otoliths from Monterey do not neces- 
sarily indicate two regions of origin. Some attributes 
of the PWP method need further study. For example, it 
is not obvious why the two equations to model otolith 
perimeters correlated differently with the weight model. 
Factors affecting otolith morphometries 
In previous studies of otolith morphology, length, area, 
and perimeter were often the most important character- 
istics that defined fish stocks (Bolles and Begg, 2000; 
Torres et al., 2000; DeVries et al., 2002; Cardinale et 
al., 2004). When included in such studies, otolith weight 
