Taylor and Gervasi: Feeding habits and dietary overlap of age-0 flounder 
181 
The diet of summer flounder described herein cor¬ 
roborate observations from the Middle and South At¬ 
lantic Bight (Packer et al., 1999); although geographic 
differences in conspecific diets are also apparent and 
are likely due to large-scale spatial variations in prey 
assemblages. For example, in the Chesapeake Bay, 
Virginia, mysid shrimp {Neomysis spp.), sand shrimp, 
mantis shrimp {Squilla empusa), and fish (bay an¬ 
chovy [Ap^choa mitchilU] and weakfish [Cynoscion 
regalis]) accounted for -91%, by weight, of the total 
diet of summer flounder 125-224 mm TL (Latour 
et al., 2008). In the York River, a major tributary of 
the Chesapeake Bay, mysid shrimp {N. americana), 
palaemonid shrimp, and fish were the favored prey of 
summer flounder 98-192 mm TL (TL converted from 
standard length [SLj; Able and Fahay, 1998) (Smith et 
al., 1984). Summer flounder 100-200 mm TL collect¬ 
ed from the Pamlico Sound, North Carolina, similar¬ 
ly ate a large volume of mysid shrimp (%V'=42%; N. 
americana), fish (38%; engraulids and sciaenids), and 
decapod shrimps (8%; carideans and penaeids) (Pow¬ 
ell and Schwartz, 1979). Conversely, in the polyha- 
line regions of the Newport and North Rivers, North 
Carolina (mean salinity: 31-32), the dominant prey of 
summer flounder 25-73 mm TL (TL converted to SL) 
were spionid polychaetes and invertebrate parts (e.g., 
clam siphons), which together composed -90% of the 
total IRI i%IRI = %N X %F; Burke, 1995). Interest¬ 
ingly, the diet composition of equivalent-size southern 
flounder (Paralichthys lethostigma), which occupied 
the lower salinity portions of Newport and North Riv¬ 
ers (mean salinity <25), was indicative of the diet 
of summer flounder examined in this study, in that 
amphipods (Gammarus spp.) and mysid shrimp (N. 
americana and Americamysis bigelowi) were the most 
important prey categories for this congener species 
(combined %IRI: -90%; Burke, 1995). 
Intraspecific diet diversity and niche breadth 
Despite the evidence that winter flounder and summer 
flounder are feeding generalists (i.e., according to cu¬ 
mulative prey taxa consumed), this study also revealed 
that certain prey contributed disproportionately to the 
diet of each species. Three prey taxa specifically ac¬ 
counted for >85% of the overall diet of both species: 
amphipods, copepods, and polychaetes (combined %IRI: 
-88%) for winter flounder and mysid shrimp, sand 
shrimp, and amphipods (combined %IRI: - 86%) for 
summer flounder. The inequitable dietary contributions 
of these favored prey were reflected in the B (values 
<0.4), where low values indicated specialized feeding 
behavior (Levins, 1968; Novakowski et al., 2008). 
Although winter and summer flounder generally are 
considered opportunistic feeders (Packer et al., 1999; 
Pereira et al., 1999), there are previous accounts of 
these species selectively foraging on prey that are in 
low abundance (Carlson et al., 1997; Shaheen et al., 
2001; Latour et ai., 2008; Meng et ah, 2008). It is im¬ 
portant to reiterate, however, that food niche breadth 
of winter and summer flounder was predator-size de¬ 
pendent, such that a moderate to high degree of diet 
diversity was observed in larger juveniles (>75 and 
115 mm TL, respectively). The broadening of dietary 
breadth with increasing lengths of winter and summer 
flounder is attributed to the concomitant enlargement 
of mouth gape and improved prey detection and cap¬ 
ture abilities in larger fish (Mulkana, 1966; Mander- 
son et al., 2000; Stehlik and Meise, 2000; Vivian et al., 
2000). Further, as observed in winter flounder, spatially 
explicit variations in niche breadth may be a reflection 
of site-specific patterns in prey diversity and availabil¬ 
ity (Mulkana, 1966; Rudnick et al., 1985); for example, 
winter flounder have a greater niche breadth in the 
Taunton River because this system possibly maintains 
a higher abundance of novel prey. 
Ontogenetic and spatiotempora! effects on intraspecific 
diets 
Direct visual analysis of the stomach contents of win¬ 
ter flounder and summer flounder affirmed ontoge¬ 
netic shifts in their respective diets. Winter flounder 
<40 mm TL predominantly fed on harpacticoid and 
calanoid copepods, transitioning to amphipods, isopods, 
and bivalves with increasing size. The principal prey of 
summer flounder <60 mm TL were mysid shrimp and 
copepods, whereas sand shrimp, amphipods, and fish 
were the dominant prey of larger conspecifics. Simi¬ 
lar size-dependent effects on feeding habits of winter 
and summer flounder have been reported throughout 
the broader geographic distribution of each species. 
In the Navesink River and Sandy Hook Bay, New Jer¬ 
sey, for example, small winter flounder (<50 mm TL) 
fed mainly on copepods (calanoids and harpacticoids), 
small polychaetes (e.g., spionids), and amphipods (e.g., 
ampeliscids) (Stehlik and Meise, 2000). Subsequent 
increases in size (50-90 mm TL) of winter flounder 
resulted in a greater reliance on amphipods and a 
dietary switch toward larger polychaetes (e.g., nerei- 
dids), mollusks (softshell [Mya arenaria] and Nassa- 
rius spp.), and other crustaceans (mysid shrimp, sand 
shrimp, and isopods) (Stehlik and Meise, 2000). Com¬ 
parable size-dependent patterns in feeding behavior of 
winter flounder were documented also in the Hudson 
River estuary, New York (20-65 mm TL; Vivian et al., 
2000), Pettaquamscutt River, Rhode Island (10-80 mm 
TL; Mulkana, 1966), and Massachusetts coastal waters 
(<25-100 mm TL; Linton, 1921). 
The diet of metamorphic summer flounder (10.4- 
18.2 mm TL, converted from SL) from the Great Bay- 
Little Egg Harbor estuary, New Jersey, was domi¬ 
nated by the calanoid copepod Temora longicornis 
(%JJ?/=86.2%), indicating a pelagic feeding strategy 
(Grover, 1998). Recently settled summer flounder also 
forage on calanoid and harpacticoid copepods in North 
Carolina coastal embayments (11.5-24.7 mm TL, con¬ 
verted from SL; Burke, 1995) and Georgia tidal creeks 
(11.5-48.6 mm TL, converted from SL; Reichert and 
van der Veer, 1991), but the use of this prey resource 
