Rulifson and Batsavage: Population demographics of Alosa mediocris 
229 
Table 4 
Proportion (%) of mature fish by sex, determined from visual inspection of gonads, and number of spawning marks by age 
class for male and female Hickory Shad ( Alosa mediocris ) collected from the Roanoke River-Albemarle Sound watershed in 
1996. n=number of fish examined. 
Age 
Males 
Females 
Percent 
mature 
Number of spawning marks 
n 
Percent 
mature 
Number of spawning marks 
n 
0 
1 
2 
3 
0 
1 
2 
3 
4 
2 
36.1 
12 
12 
38.5 
7 
7 
3 
97.9 
92 
56 
148 
93.9 
38 
24 
62 
4 
99.6 
4 
50 
14 
68 
98.6 
6 
69 
48 
123 
5 
100 
1 
0 
1 
2 
4 
100 
2 
4 
9 
3 
18 
6 
100 
0 
0 
0 
1 
1 
100 
0 
0 
0 
1 
0 
1 
7 
100 
0 
0 
1 
0 
1 
2 
n examined 
233 
109 
106 
15 
3 
233 
213 
53 
97 
58 
4 
1 
213 
Proportion 
(%) of total 
population 
46.8 
45.5 
6.4 
1.3 
24.9 
45.5 
27.2 
1.9 
0.5 
bemarle Sound (n= 74, f=-1.570, P=-0.120), indicating 
that both sexes feed extensively in ocean waters be- 
fore entering the phase of inland spawning migration. 
There were weak positive relationships between somat- 
ic weight and mesentery fat for both males (r 2 =0.17) 
and females (r 2 =0.29) in the Albemarle Sound, but 
these relationships essentially disappeared (males: 
r 2 =0.14; females: r 2 =0.02) on the spawning grounds in 
the Roanoke River (Fig. 5). 
Interestingly, a similar set of relationships was ob- 
served between gonad weight and mesentery fat in 
males and females (males: P 2 =0.46; females: P 2 =0.21) 
in the Albemarle Sound — relationships that disap- 
peared (males: P 2 =0.20; females: f? 2 =0.05) on the 
spawning grounds (Fig. 6), indicating that fish were 
using mesentery fat during their upsti’eam migration 
for metabolic energy and not for increasing gonad size. 
For gut analysis, the stomachs of 212 fish were ex- 
amined. Of the fish collected from the Albemarle Sound 
and Roanoke River, 26% (62) and 28% (110), respec- 
tively, contained identifiable items. In fish from both 
locations, 83% of stomach items found fitted into 5 
categories: fish (Clupeidae), parasites (Isopoda), seeds, 
wood, and plastic. Insects, a sixth category, were found 
only in stomachs of Roanoke River fish. 
Discussion 
Adult sex ratios 
The sex ratios in our study indicated that there was no 
sex-selective harvest by anglers in 1996. The male-to- 
female ratios from near the Roanoke River spawning 
grounds at Weldon (0.76:1) indicated that slightly more 
females than males were sampled. A similar result 
(0.73:1) was obtained from the NCDMF Independent 
Gill Net Survey of Striped Bass in the Albemarle Sound 
, but the independent gillnet survey in the RRNWR se- 
lected for male fish (4.29:1). The RRNWR survey used 
small mesh sizes, causing bias toward smaller males; 
the gillnet survey in Albemarle Sound for Striped Bass 
used a wide range of mesh sizes to allow for collection 
of the full size range of both sexes. 
In some cases, males were more abundant than fe- 
males because a greater proportion of males reach ma- 
turity at an earlier age; moreover, differential arrival 
periods of males and females on the spawning grounds, 
as in the Chesapeake Bay, can affect the sex ratios 
found in samples (Klauda et al. 1991a). Pate (1972) 
found the male-to-female ratio to be 4:1 for Hickory 
Shad sampled by a nonselective haul seine in the Neu- 
se River, North Carolina. This ratio could have been 
the result of recruitment of a large proportion of virgin 
males to the spawning population (47.3% of the males 
were age 2). 
Skewness of true sex ratios from increased mortal- 
ity of a targeted sex likely plays a role in population 
rebuilding. For Alosa species, females are obviously 
the limiting factor, and older age classes have greater 
reproductive potential. Higher rates of survival to re- 
peat-spawning age and a sex ratio closer to 1:1 should 
lead to accelerated population rebuilding, as opposed to 
the rebuilding potential of a population with far more 
males and virgin spawners. Some alosine fisheries (e.g., 
American Shad) target females for their roe (Rulifson 
et al., 1982), and such activity will shift the true sex 
ratio. 
