668 
Fishery Bulletin 99(4) 
Table 1 
(continued) 
Frequency 
(stomachs) 
%F 
Number 
(counts) 
%N 
Volume 
(mL) 
%V 
IRI 
Family Uranoscopidae (continued) 
Astroscopus sp. 1 
1.28 
1 
0.14 
40 
0.34 
1 
UnID Pleuronectiformes 
3 
3.85 
4 
0.56 
5 
0.04 
2 
Family Bothidae 
Paralichthyes dentatus 
2 
2.56 
2 
0.28 
25 
0.21 
1 
Scopthalamus aquosus 
1 
1.28 
1 
0.14 
15 
0.13 
0 
UnID Bothidae 
1 
1.28 
1 
0.14 
2 
0.02 
0 
Family Soleidae 
Trinectes maculatus 
9 
11.54 
14 
1.97 
440 
3.74 
66 
UnID Soleidae 
3 
3.85 
3 
0.42 
15 
0.13 
2 
Family Diodontidae 
Chilomycterus schoepfi 
3 
3.85 
3 
0.42 
15 
0.13 
2 
Totals 
712 
11754 
Table 2 
Consumption of portunid crabs as a function of five cobia size classes in lower Chesapeake Bay. 
Cobia size class (cm FL) 
<100 
100-109.9 
110-119.9 
120-129.9 
>130 
Callinectes sapidus 
n 
9 
16 
12 
23 
42 
Mean carapace width (mm) 
55.2 
72.3 
75.0 
116.7 
94.7 
Range of carapace width (mm) 
33-86 
42-120 
45-120 
42-120 
35-120 
Ovalipes ocellatus 
n 
42 
37 
38 
32 
27 
Mean carapace width (mm) 
39.1 
41.2 
37.7 
45.3 
37.1 
Range of carapace width ( mm ) 
26-50 
30-56 
20-51 
20-51 
27-55 
ly the jaw plates (22-49 mm width) remained; thus, the 
IRI for cownose ray is likely underestimated. Flatfishes 
and syngnathids represented the teleosts most frequently 
consumed by cobia in Chesapeake Bay and North Caroli- 
na. Hogchoker ( Trinectes maculatus ) was more frequently 
consumed by cobia in Chesapeake Bay (our study) than 
in North Carolina (Smith, 1995). Blackcheek tonguefish 
( Symphurus plaigusa) was regularly consumed by cobia in 
North Carolina (Smith, 1995) but was absent from cobia 
stomachs in Chesapeake Bay. In Chesapeake Bay, Syngna- 
thus sp. (pipefish) and Hippocampus sp. (seahorse) were 
only important in the diet of smaller cobia, whereas in 
North Carolina, these fishes were important in the diet of 
all cobia (Smith, 1995). 
Cobia in our study predominantly consumed benthic 
and epibenthic prey items, most notably portunid crabs. 
Feeding studies on other large predatory fishes in Chesa- 
peake Bay during the summer months, such as bluefish, 
Pomatomous saltatj'ix, and weakfish, Cynoscion regalis, 
reveal that these species consume prey items associated 
predominantly with pelagic food webs (Hartman and 
Brandt, 1995a, 1995b). Striped bass, Morone saxatalis, a 
large predator present in Chesapeake Bay year-round, 
is also reported to feed predominantly on pelagic fishes 
(Hartman and Brandt, 1995a, 1995b; Walters, 1999). 
During the summer, portunid crabs were consumed by 
bluefish, weakfish, and striped bass in Chesapeake Bay; 
however, portunid crab consumption was typically less 
than 5% of total prey items present in the stomachs of 
these fishes (Hartman and Brandt, 1995a, 1995b; Wal- 
ters, 1999). Red drum, Sciaenops ocellatus, a large pred- 
ator that uses Chesapeake Bay between spring and fall 
is also reported to selectively consume portunid crabs 
in estuarine environments in the Gulf of Mexico (Scharf 
and Schlict, 2000); however, feeding habits of red drum 
in Chesapeake Bay have not been documented. Although 
