112 
Fishery Bulletin 108(1) 
Table 1 
Multivariate analysis of covariance (MANCOVA) of the relationships among the dependent variables, received sound level and 
peak acoustic frequency of Atlantic croaker ( Micropogonias undulatus ) calls; the covariates dissolved oxygen concentration ( DO), 
temperature (Temp), and trawl catch per unit of effort for Atlantic croaker (CPUE); and fixed factors of month and habitat and 
their interaction in North Carolina’s Neuse River estuary (test statistic = Hotelling’s trace statistic). 
Effect 
Test statistic 
F 
Hypothesis df 
Error df 
P 
Partial rj 2 1 
Power 
Intercept 
0.812 
50.75 
2 
125 
0.000 
0.45 
1.00 
DO 
0.067 
4.21 
2 
125 
0.017 
0.06 
0.73 
Temp 
0.122 
7.63 
2 
125 
0.001 
0.11 
0.94 
CPUE 
0.05 
3.13 
2 
125 
0.047 
0.05 
0.59 
Month 
0.078 
1.62 
6 
248 
0.142 
0.04 
0.62 
Habitat 
0.072 
2.25 
4 
248 
0.065 
0.04 
0.65 
Month x Habitat 
0.155 
1.60 
12 
248 
0.092 
0.07 
0.83 
1 Partial q 2 is a standard measure of effect size (the proportion of variance in the dependent variable that is attributable to the independent vari- 
able, after partialling out the other independent variables). It varies between 0 and 1, and its meaning is similar to that of an R 2 in multiple 
regression or multiple correlation (Zar, 1999, p. 319). 
Table 2 
Between-subject effects from a multivariate analysis of covariance (MANCOVA) to investigate the relationships among the 
dependent variables received sound level (Level) and peak acoustic frequency (Frequency) of Atlantic croaker (Micropogonias 
undulatus) calls; the covariates dissolved oxygen concentration (DO), temperature (Temp), and trawl catch per unit of effort 
of Atlantic croaker (CPUE); and fixed factors of month and habitat, and their interaction in North Carolina’s Neuse River 
estuary. 
Source 
Dependent variable 
df 
F 
P 
Partial rf 1 
Power 
Corrected model 
Level 2 
14 
4.97 
0.000 
0.36 
1.00 
Frequency 3 
14 
2.74 
0.001 
0.23 
0.99 
Intercept 
Level 
1 
56.29 
0.000 
0.31 
1.00 
Frequency 
1 
12.33 
0.001 
0.09 
0.94 
DO 
Level 
1 
7.69 
0.006 
0.06 
0.79 
Frequency 
1 
3.44 
0.066 
0.03 
0.45 
Temp 
Level 
1 
6.30 
0.013 
0.05 
0.70 
Frequency 
1 
3.48 
0.064 
0.03 
0.46 
CPUE 
Level 
1 
2.55 
0.113 
0.02 
0.35 
Frequency 
1 
1.46 
0.229 
0.01 
0.22 
Month 
Level 
3 
1.54 
0.208 
0.04 
0.40 
Frequency 
3 
1.60 
0.193 
0.04 
0.41 
Habitat 
Level 
2 
4.55 
0.012 
0.07 
0.77 
Frequency 
2 
0.67 
0.513 
0.01 
0.16 
Month x Habitat 
Level 
6 
1.08 
0.377 
0.05 
0.41 
Frequency 
6 
2.31 
0.038 
0.10 
0.78 
1 Partial rj 2 is a standard measure of effect size (the proportion of variance in the dependent variable that is attributable to the independent vari- 
able, after partialling out the other independent variables). It varies between 0 and 1, and its meaning is similar to that of an R 2 in multiple 
regression or multiple correlation (Zar, 1999, p. 319). 
2 Type-III sum of squares: R 2 =0 . 356 (adjusted R 2 =0. 284) 
3 Type-III sum of squares: R 2 =0 . 233 (adjusted R 2 =0. 148) 
distance to creek were also significantly correlated with 
Atlantic croaker density (Fig. 3). Catch rates of Atlantic 
croaker were significantly higher before June 11 (day 
161) than were those later in the summer or fall, and 
catch rates were significantly higher within 525 m of 
the creeks than they were beyond this distance. 
Discussion 
The global MANCOVA test found trawl CPUE to be a 
significant factor (Table 1). But the MANCOVA test of 
between-subject correspondence failed to detect any sig- 
nificant relationship between CPUE and received sound 
