NOTE Arendt et al.: Stomach content analysis of Rachycentron cancidum 
667 
Table 1 
Index of relative importance (IRI) of prey items consumed by cobia (n= 78) in lower Chesapeake Bay, June-July 1997. IRI was 
calculated as (% Number + % Volume ) x (% Frequency), as described in Smith ( 1995) and Meyer and Franks (1996). Frequency ( %F ) 
is the percent of stomachs that contained food. UnID = unidentified. 
Frequency 
(stomachs) 
%F 
Number 
(counts) 
%N 
Volume 
(mL) 
%V 
IRI 
Phylum Cnidaria 
Class Hydrozoa 
Family Sertulariidae 
Sertularia sp. 
1 
1.28 
1 
0.14 
8 
0.07 
0 
Phylum Mollusca 
Class Bivalva 
Family Mytilidea 
Mytilus edulis 
2 
2.56 
47 
6.60 
17 
0.14 
17 
Phylum Arthropoda 
Class Crustacea 
Family Squillidae 
Squilla empusa 
2 
2.56 
2 
0.28 
11 
0.09 
1 
Family Pagruidae 
3 
3.85 
3 
0.42 
5 
0.04 
2 
Family Portunidae 
Callinectes sapidus 
46 
58.97 
226 
31.74 
6736 
57.31 
5252 
Ovalipes ocellatus 
43 
55.13 
321 
45.08 
2505 
21.31 
3660 
Family Canceridae 
Cancer sp. 
2 
2.56 
2 
0.28 
26 
0.22 
1 
Cancer irroratus 
1 
1.28 
1 
0.14 
5 
0.04 
0 
Family Xanthidae 
Neopanope sp. 
1 
1.28 
3 
0.42 
5 
0.04 
1 
Phylum Chordata 
Class Chonrichthyes 
Family Myliobatidae 
Rhinoptera bonasus 
7 
8.97 
8 
1.12 
81 
0.69 
16 
Class Osteichthyes 
Family Clupeidae 
Opisthonema oglinum 
1 
1.28 
3 
0.42 
160 
1.36 
2 
Brevoortia tyrannus 
1 
1.28 
1 
0.14 
180 
1.53 
2 
UnID Clupeidae 
2 
2.56 
2 
0.28 
275 
2.34 
7 
Family Batrachoididae 
Opsanus tau 
1 
1.28 
1 
0.14 
185 
1.57 
2 
Family Ophidiidae 
Ophidion marginatum 
1 
1.28 
1 
0.14 
42 
0.36 
1 
Ophidion sp. 
3 
3.85 
4 
0.56 
47 
0.40 
4 
Family Sygnathidae 
Syngnathus floridae 
1 
1.28 
1 
0.14 
2 
0.02 
0 
Syngnathus sp. 
2 
2.56 
2 
0.28 
9 
0.08 
1 
Hippocampus erectus 
1 
1.28 
1 
0.14 
3 
0.03 
0 
Hippocampus sp. 
5 
6.41 
49 
6.88 
52 
0.44 
47 
Family Pomatomidae 
Pomatomus saltatrix 
1 
1.28 
1 
0.14 
180 
1.53 
2 
Family Sciaenidae 
Micropogonias undulatus 
3 
3.85 
3 
0.42 
663 
5.64 
23 
Family Uranoscopidae 
continued 
