Willis et al Feeding behavior of 3 sciaenids along the southeastern United States 
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■■■ Weakfish 
l l Southern kingfish 
r . ,..i Atlantic croaker 
Weakfish 
Southern kingfish 
W Atlantic croaker 
jr j?' rf & 
& <t 
Figyre 2 
For weakfish (Cynoscion regalis; n = 276), southern kingfish 
( Menticirrhus americanus', n=408), and Atlantic croaker ( Mi - 
cropogonias undulatus; n=351) captured in 2008, 2009, and 
2010 off the Atlantic coast of the southeastern United States, 
(A) mean diet composition by weight (%MW) and (B) mean 
diet composition by number (%MN) by prey category: decapod 
crustaceans, echinoderms, bony fishes, mollusks, nondecapod 
crustaceans, polychaetes, and other (composed of unidentified 
animal tissue and rarely seen miscellaneous taxa). Error bars 
indicate 1 standard deviation of the mean. 
pies contained decapod crustaceans 68% of the time 
and nondecapod crustaceans 62% of the time (Table 2). 
Polychaetes were identified in more than 40% of south- 
ern kingfish stomachs. Identified polychaetes included 
representatives from 20 different families, primar- 
ily Ampharetidae, Glyceridae, Nephtydae, Onuphidae, 
Opheliidae, and Terebellidae. Decapod crustaceans com- 
posed 33% of the composition by weight of the southern 
kingfish diet. Composition by number was higher 
for nondecapod crustaceans (41%) than for deca- 
pod crustaceans (31%). Mean percent weight and 
mean percent number were highest for decapod 
crustaceans (39% and 36%, respectively), com- 
pared with the mean values for all other prey 
categories. Polychaetes had the second-highest 
mean percent weight (23%), whereas nondecapod 
crustaceans represented 17% of the diet (Fig. 2, 
A and B). 
Amundsen metrics indicate that the popula- 
tion of southern kingfish displayed a generalized 
feeding strategy. Although some prey items, in- 
cluding mysids, gammaridean amphipods, and 
cumaceans, were consumed regularly, most prey 
types were infrequently observed in the stomachs 
of southern kingfish (Fig. 3B). The concentra- 
tion of data points along the y-axis in Figure 3B 
is indicative of prey items that were present in 
the stomachs of individual southern kingfish but 
were rarely if ever seen in the stomachs of more 
than a single animal. 
Atlantic croaker 
Of the 421 Atlantic croaker selected for diet 
analysis (with an average size of 18 cm TL for 
young-of-the-year fish through adult fish), 351 in- 
dividuals had stomachs that contained prey items 
(83%; Table 1). Prey representing 91 taxa were 
identified (Table 2). 
Nondecapod crustaceans (56%) and polychaetes 
(51%) were the prey categories with the highest 
frequencies of occurrence in the diet of Atlantic 
croaker in this study (Table 2). Decapod crusta- 
ceans (45%) were the third most frequent prey 
category. Values of composition by weight were 
comparable for bony fishes, decapods crustaceans, 
and polychaetes (21%, 22%, and 29%, respective- 
ly). Nondecapod crustaceans, most of which were 
mysids, had the highest value of composition by 
number (54%). Across all sampling years, poly- 
chaetes dominated mean percent weight, compos- 
ing 30% of the prey weight (Fig. 2A). However, 
nondecapod crustaceans were numerically domi- 
nant, accounting for 30% of the number of prey 
(Fig. 2B). 
Atlantic croaker were the most general- 
ized feeders of the 3 sciaenids, according to the 
Amundsen plot in Figure 3C. Most of the data 
points in this figure appear along the y-axis, 
indicating that individual Atlantic croaker con- 
sumed many different prey types and that those prey 
types were rarely seen in the stomachs of other in- 
dividual fish. The data points in the center of this 
graph indicate those prey that were more frequently 
found in the stomachs of Atlantic croaker than in 
the stomachs of the other 2 species: mysid shrimp, 
various unidentified crustacean parts, and gammarid- 
ean amphipods. 
