Schlick and de Mutsert: Growth of adult river herring that spawn in tributaries of the Potomac River 
63 
Table 1 
The equations used to convert between values of standard length (SL), fork 
length (FL), and total length (TL) in millimeters for alewife (Alosa pseudo- 
harengus) and blueback herring (Alosa aestivalis) captured from tributaries 
of the Potomac River in northern Virginia during 2007-2015. Also provided 
are coefficients of multiple determination (R 2 ), or proportions of variance, to 
indicate the correlation between variables used to determine the equations. 
Species 
Conversion 
Equation 
n 
R 2 
Alewife 
SL to FL 
FL=1.0076(SL>+18.832 
1056 
0.920 
Alewife 
SL to TL 
TL=1.0922(SL)+31.529 
1002 
0.873 
Alewife 
FL to TL 
7X=0.9852(FL 1+33.807 
1001 
0.968 
Blueback 
SL to FL 
FL=1.0208(SL)+14.675 
630 
0.928 
Blueback 
SL to TL 
TL=1.14461SL 1+18.644 
630 
0.930 
Blueback 
FL to TL 
TL= 1.104(FL)+6.02 
630 
0.972 
Length-length relationship 
Alewife had a mean SL of 210.8 mm (standard devia¬ 
tion [SD] 13.57), mean FL of 231.2 mm (SD 14.25), 
and mean TL of 261.9 mm (SD 15.85). Blueback her¬ 
ring had a mean SL of 202.1 mm (SD 11.80), mean FL 
of 221.0 mm (SD 12.51), and mean TL of 250.0 mm 
(SD 14.00). The relationships between SL, FL, and TL 
were highly significant for alewife and blueback her¬ 
ring (with all proportions of variance, or coefficients of 
multiple determination, >0.85; Table 1). 
Aging 
Alewife Otoliths were collected from 574 alewife over 
9 consecutive years (2007-2015), and readers agreed 
on all ages except for 1 alewife. Ages ranged from 
2 to 7 years with a median age of 3 years for both 
females (n=244) and males (n=329). Scales could be 
read for 532 of the 574 dissected alewife. Scale ag¬ 
ing revealed reader bias, particularly in younger 
ages. Fish aged as 2 and 3 years old from scale read¬ 
ings commonly had younger ages that the 2 readers 
agreed upon from their otolith analyses, and fish as¬ 
signed ages of 5, 6, and 7 years from scale analyses 
commonly had older age estimates from otolith read¬ 
ings; however, for fish at ages of 4, 6, and 7 years 
based on scale readings, estimates were not statisti¬ 
cally different from ages based on otolith analyses 
(Table 2). Biases in ages between scale and otolith 
readings were statistically different in the McNe- 
mar’s, Evans-Hoenig, and Bowker’s tests: P=0.0032, 
P=0.0089, P=0.0001, respectively. Ages determined 
with the use of scales and otoliths agreed for 83.1% 
of the samples and were within 1 year of each other 
for an additional 15.0% of samples, with an ACV of 
3.8%, indicating that the ages were precise according 
to standards established by Campana (2001). 
Blueback herring Blueback herring were sampled from 
2007 through 2015, but none were captured in 2009 
and 2010. Otolith readers agreed on ages for 285 of 
Table 2 
The number of samples for each comparison of ages between otolith and scale readings for ale¬ 
wife (Alosa pseudoharengus) captured between 2007and 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 different from the age determined 
by reading otoliths. 
Scale age 
Otolith age 
2 
3 
4 
5 
6 
7 
t 
P 
2 
16 
22 
1 
1 
6.51 
<0.0001* 
3 
- 
222 
20 
2 
2 
- 
4.60 
<0.0001* 
4 
- 
10 
140 
8 
- 
— 
-0.47 
0.6388 
5 
- 
- 
14 
49 
2 
- 
-3.21 
0.0084* 
6 
- 
- 
2 
2 
11 
1 
-1.58 
0.2824 
7 
— 
— 
— 
2 
1 
4 
-1.99 
0.2824 
