64 
Fishery Bulletin 11 7(1-2) 
Table 3 
The number of samples for each comparison of ages between otolith and scale readings for 
blueback herring {Alosa aestivalis ) captured in 2007 and 2008 and between 2011 and 2015 in 
the Potomac River in northern Virginia, with t-test statistics (t) to indicate bias for each age. 
An asterisk (*) indicates when the ages determined by reading scales were significantly dif¬ 
ferent from the age determined by reading otoliths. 
Scale age 
Otolith age 
2 
3 
4 
5 
6 
t 
P 
2 
41 
13 
_ 
_ 
_ 
4.10 
0.0007* 
3 
- 
143 
12 
- 
- 
3.63 
0.0151* 
4 
- 
1 
32 
- 
- 
-1.00 
0.6496 
5 
- 
3 
2 
8 
- 
-2.55 
0.0762 
6 
- 
— 
1 
— 
3 
-1.00 
0.6496 
287 samples. Ages ranged from 2 to 6 years, with a 
median age of 3 years for both females (n = 123) and 
males (/? = 164). Scales could be read for 260 of 287 
dissected blueback herring, with the ages of 2 and 3 
years commonly overaged by readers and statistical¬ 
ly biased on the basis of McNemar’s, Evans-Hoenig, 
and Bowker’s tests (all tests: P<0.0001; Table 3). Ages 
agreed between scale and otolith readings for 87.3% 
of the samples and were within 1 year of each other 
for an additional 10.8% of the samples. The ACV was 
3.2%, indicating that the aging of samples were precise 
(Campana, 2001). 
Growth models 
The best-fit model for alewife was the linear growth 
model, and the worst-fit model was the Richards 
growth model (Table 4). The best-fit model for blue- 
back herring was the logistic growth model, and the 
worst-fit model was the linear growth model (Table 4). 
However, the AIC weights were only 10.6% and 10.5% 
different between the best-fit and worst-fit models for 
alewife and blueback herring, respectively (Table 4). 
For this reason, the von Bertalanffy growth function, 
the most traditionally used growth model, was used to 
Table 4 
Rank of Akaike’s information criterion weights ( w ) calculated for alewife (Alosa pseudoharengus) and 
blueback herring (Alosa aestivalis) based on sample size (n), number of parameters ( k ), sums of squares 
(SSQ), and Akaike’s information criterion for model selection (AIC;) from each growth model used in this 
study. 
Species Growth model 
n 
k 
SSQ 
AIC; 
w (%) 
Rank 
Alewife Cerrato 
559 
3 
96,589 
1702.954 
11.432 
5 
Francis 
559 
3 
96,589 
1702.954 
11.432 
5 
Gompertz 
559 
3 
96,582 
1702.936 
11.533 
3 
Laird-Gompertz 
559 
3 
96,582 
1702.936 
11.533 
3 
Linear 
559 
2 
97,165 
1702.398 
15.093 
1 
Logistic 
559 
3 
96,576 
1702.921 
11.621 
2 
Ratkowsky 
559 
3 
96,589 
1702.954 
11.432 
5 
Richards 
559 
4 
96,537 
1704.823 
4.490 
9 
von Bertalanffy 
559 
3 
96,589 
1,702.954 
11.432 
5 
Blueback herring Cerrato 
285 
3 
34,956 
828.756 
13.170 
4 
Francis 
285 
3 
34,956 
828.754 
4.914 
8 
Gompertz 
285 
3 
34,955 
828.751 
13.170 
4 
Laird-Gompertz 
285 
3 
34,955 
828.751 
13.193 
2 
Linear 
285 
2 
36,429 
831.863 
2.782 
9 
Logistic 
285 
3 
34,953 
828.744 
13.240 
1 
Ratkowsky 
285 
3 
34,956 
828.754 
13.170 
4 
Richards 
285 
4 
34,948 
830.726 
13.193 
2 
von Bertalanffy 
285 
3 
34,956 
828.754 
13.170 
4 
