Rulifson and Batsavage: Population demographics of Alosa mediocris 
231 
Table 5 
Number of ova, estimated gravimetrically and from regressions developed for age, in 
ovaries of female Hickory Shad (Alosa mediocris ), collected in Albemarle Sound and 
the Roanoke River in 1996, and mean values of the following variables: fork length 
(FL) measured in millimeters, body weight (BWT) measured in grams, and somatic 
weight (SWT) measured in grams at age, measured in years. «=number of ovaries 
examined. 
Age 
n 
Gravimetric 
counts 
(observed) 
Counts 
on basis 
of age 
Counts by 
mean FL 
at age 
Counts by 
mean BWT 
at age 
Counts by 
mean SWT 
at age 
2 
i 
85,803 
108,012 
138,195 
113,366 
121,109 
3 
14 
137,523 
147,267 
154,849 
132,642 
144,776 
4 
19 
223,576 
200,787 
211,380 
196,382 
207,344 
5 
3 
294,798 
273,758 
221,275 
217,874 
228,758 
6 
1 
478,944 
373,249 
410,929 
411,646 
442,326 
7 
2 
250,918 
508,897 
391,352 
367,134 
378,751 
quencies. Other studies on 
Hickory Shad and other 
Alosa species also showed a 
significant degree of overlap 
of lengths at age (Street and 
Adams 15 ; Pate, 1972; NCD- 
MF 21 ). Our results indicate 
that the mean FLs at age for 
both sexes from age 3 and 
older were smaller than the 
means reported from ear- 
lier investigations. This dif- 
ference could be the result 
of 1) the capture method 
used by previous investiga- 
tors, who collected Hickory 
Shad in gill nets with large 
mesh sizes that were set for 
American Shad (Street et 
al. 4 ; Hawkins 8 ), 2) the scales 
used for determining age, 
or 3) both. Pate (1972) ex- 
amined Hickory Shad captured in a nonselective haul 
seine and found that the largest Hickory Shad of both 
sexes were the oldest fish sampled (ages 5-7). 
The mean FLs from back calculations with both the 
Dahl-Lea direct proportion method and the von Berta- 
lanffy growth equation indicate that the smaller age-2 
Hickory Shad were not part of the spawning migra- 
tion. The largest differences between mean observed 
FLs and mean back-calculated FLs from the von Ber- 
talanffy growth equation occurred at age 2 (Table 2). 
The only age-2 fish sampled were the ones that were 
sexually mature. Analysis of spawning marks showed 
that approximately 41% of age-2 Hickory Shad (sexes 
combined) were mature at this age, indicating that the 
majority of age-2 Hickory Shad were not sampled. It is 
presumed that age-1 fish and many age-2 fish remain 
at sea, but this portion of the lifecycle is unknown. 
Annual mortality rates were higher in this study 
(0.75, sexes combined) than in previous studies in Al- 
bemarle Sound; rates from other studies ranged from 
0.40 to 0.65 (Street et al. 4 ; Johnson et al. 22 ). However, 
it should be noted that the annual mortality in those 
studies was calculated with the Robson and Chapman 
(1961) method that computes survival instead of us- 
ing the catch curve to estimate mortality. Our mortal- 
ity rates were higher for females (0.83) than for males 
(0.76). Because the catch curve was generated from 
just 1 year of data, it is difficult to determine the cause 
for higher mortality estimates. Moderate fluctuations 
22 Johnson, H. B„ D. W. Crocker, B. F. Holland Jr., J. W. Gil- 
liken, D. L. Taylor, M. W. Street, J. G. Loesch, W. H. Rrete Jr., 
and J. G. Travelstead. 1978. Biology and management of 
mid-Atlantic anadromous fishes under extended jurisdiction. 
Completion Report AFCS-9-2, 175 p. Division of Marine 
Fisheries, North Carolina Department of Natural Resources 
and Community Development, Morehead City, NC, and Vir- 
ginia Institute of Marine Science, Gloucester Point, VA. 
in annual recruitment are common in fish populations, 
but catch curves derived from 2 or more years of data 
can reduce the effects of variable recruitment (Ricker, 
1975). 
Spawning history and reproductive analysis 
The short lifespan of Hickory Shad, combined with 
an early age to maturity and an anadromous migra- 
tion pattern, indicates that adult fish in the Albemarle 
Sound-Roanoke River population are subject to rec- 
reational (sound and inland waters) and commercial 
harvest (sound and ocean waters) for 1 or 2 seasons 
before they are removed by harvest or natural mortal- 
ity. Approximately one-third of both sexes are sexually 
mature as early as age 2, >93% of the population is 
mature by age 3, and essentially 100% of the popula- 
tion is mature by age 4 (Table 4). One or 2 spawning 
marks on the scales examined were common, but 3 or 
more marks were rare. These results were similar to 
findings for Hickory Shad in the Altamaha River, Geor- 
gia (Street, 1970), the Neuse River (Pate, 1972), and 
more recently the Tar- Pamlico River (Murauskas and 
Rulifson, 2011). 
On the basis of age to maturity and spawning pat- 
terns, Hickory Shad and American Shad are exploited 
similarly in the Albemarle Sound region, but the level 
of exploitation for these species differs south of Cape 
Hatteras. American Shad in Albemarle Sound usually 
reach sexual maturity by age 3 or age 4 for males and 
by age 4 or age 5 for females. Both sexes spawned up 
to 3 times (Winslow 19 ’ 20 ). American Shad show a lati- 
tudinal gradient between semelparity and iteroparity 
throughout its range (Leggett and Carscadden, 1978). 
In contrast, individual American Shad in populations 
south of Cape Hatteras seldom spawn more than once, 
and adults in populations in New York and Connecticut 
