Schlick and de Mutsert: Growth of adult river herring that spawn in tributaries of the Potomac River 
61 
Figure 1 
Map of locations where adult river herring, alewife (Alosa pseu- 
doharengus ) and blueback herring (Alosa aestivalis ), were sam¬ 
pled from 2007 through 2015 within small tributaries that lead 
to the Potomac River in northern Virginia. There are 5 locations: 
Quantico Creek, Pohick Creek, Accotink Creek, Dogue Creek, 
and Cameron Run. Map data sources: U.S. Geological Survey, 
1:250,000-scale Hydrologic Units of the United States; Esri, U.S. 
National Atlas Water Feature Lines. 
line, and overall health of river herring popu¬ 
lations, whose current statuses are unknown. 
Materials and methods 
Study sites 
Adult river herring were sampled at 5 loca¬ 
tions: Pohick Creek, Accotink Creek, Dogue 
Creek, Quantico Creek, and Cameron Run, all 
third-order tributaries that run through north¬ 
ern Virginia and drain into the Potomac River 
south of Washington, D.C. (Fig. 1). This stretch 
of the Potomac River is tidally influenced fresh¬ 
water, which continues into the lower portions 
of each creek (Jones et al., 2008). River her¬ 
ring have been documented to spawn in each 
creek below the Virginia fall line (Jones et al. 9 ; 
Schlick, 2016; Jones et al. 5 ). 
Field methods 
Adults migrating upstream through Accotink 
Creek and Pohick Creek (Fig. 1) were sampled 
by blocking each creek for 24 h by using a hoop 
net with a mesh of 1.3 cm and snow fencing 
with a mesh of 5.1 cm once a week from mid- 
March through May from 2007 through 2015. 
Cameron Run was sampled the same way from 
2013 through 2015 (Fig. 1). In 2007 and 2008, 
adult river herring were collected from Quan¬ 
tico Creek and Dogue Creek by electrofishing 
(Fig. 1). All captured adult alewife (/?.=1707) 
and blueback herring (n=1159) were counted 
and measured, and their sex was determined. 
Adults that did not survive capture (598 ale¬ 
wife and 304 blueback herring) were frozen un¬ 
less dissection occurred within 48 h of capture. 
Adults were measured for wet weight in grams 
and for standard length (SL), fork length (FL), 
and total length (TL) in millimeters. Scales 
were collected, cleaned by using a mild deter¬ 
gent, and dried flat (ASMFC 8 ). Sagittal otoliths 
were collected and stored dry. 
Laboratory methods 
Sagittal otoliths were cleaned of all fish debris by us¬ 
ing water. Two separate readers viewed otoliths under 
a dissecting microscope on a black background by using 
reflected light following procedures outlined in the re¬ 
port of the ASFMC workshop on aging of river herring 
held in 2013 (ASMFC 8 ). Samples were excluded from 
analysis when an age was not agreed upon. From each 
9 Jones, R. C., K. de Mutsert, and G. D. Foster. 2014. An 
ecological study of Hunting Creek 2013: final report, 113 
p. George Mason Univ., Fairfax, VA. [Available from web¬ 
site.) 
fish, 5-6 scales were cleaned with water and a mild de¬ 
tergent; then they were sandwiched between 2 slides, 
examined, photographed by using a camera mounted 
on a dissecting microscope with transmitted light, and 
read for annuli (ASMFC 8 ). Because river herring were 
captured during spawning season, the edges of otoliths 
and scales were counted as a year (Cating, 1953). 
Age validation 
It was assumed that ages from analysis of otoliths were 
more likely to be accurate than ages from analysis of 
scales because scales contain more false annuli and are 
more susceptible to environmental degradation (Cam- 
pana and Neilson, 1985; Beamish and McFarlane, 1987; 
Besler, 1999). Additionally, readers agreed on 858 of 861 
