182 
Fishery Bulletin 115(2) 
diminished rapidly as the body size of summer floun¬ 
der increased. Numerous studies have also reported 
the signiflcance of mysid shrimp in the diet of juvenile 
summer flounder throughout the geographic range of 
this species (from New York to Georgia: Kimmel, 1973; 
Smith and Daiber, 1977; Festa^; Powell and Schwartz, 
1979; Lascara, 1981; Wenner et al.®; Reichert and van 
der Veer, 1991; Burke, 1995; Timmons, 1995; Mander- 
son et ah, 2000; Link et ah, 2002; Latour et ah, 2008; 
Buchheister and Latour, 2011; Sagarese et ah, 2011). 
However, the dietary contributions of mysid shrimp 
typically declined with the increasing size of summer 
flounder, and this prey resource was replaced by other 
macrocrustaceans (sand shrimp, mantis shrimp, and 
crabs), flsh, and squid (Powell and Schwartz, 1979; 
Link et ah, 2002; Latour et ah, 2008; Buchheister and 
Latour, 2011). 
Significant spatiotemporal variability was observed 
in the diet composition of winter and summer floun¬ 
der in this study. These observed patterns may be 
partly attributed to differences in the size structure 
of winter and summer flounder across riverine sites 
and to progressive increases in body size over time 
(Taylor et ah, 2016)—the latter resulting in ontoge¬ 
netic dietary shifts, as described above. Alternatively, 
the observed food habits of winter and summer floun¬ 
der may reflect habitat and seasonal variations in 
prey composition (Rudnick et ah, 1985; Meng et ah, 
2008), which have previously been reported to affect 
the diet of both species (Mulkana, 1966; Burke, 1995; 
Manderson et ah, 2000; Stehlik and Meise, 2000; La¬ 
tour et ah, 2008). Spatiotemporal variations in prey 
assemblages were not assessed in this study; however, 
prior investigations in the Narragansett Bay have re¬ 
vealed substantial changes in abundances of benthic 
meiofauna and macrofauna across sites and seasons 
(Rudnick et ah, 1985; Calabretta and Oviatt, 2008), 
and some of these fauna constitute important prey for 
juvenile winter and summer flounder (e.g., harpacti- 
coid copepods, polychaetes, nematodes, and bivalves). 
Interspecific dietary overlap 
The feeding habits of winter flounder and summer 
flounder differed significantly from each other, but the 
extent of dietary overlap was affected by their respec¬ 
tive body sizes. According to assessments with the 
Schoener index, there was minimal dietary overlap 
of flounder species when comparisons were made in¬ 
dependent of body size (a<0.4; Hartman and Brandt, 
® Festa, R J. 1979. Analysis of the fish forage base 
of the Little Egg Harbor estuary. N.J. Dep. Environ. 
Prot., Tech. Rep. 24M, 134 p. [Available from web¬ 
site.] 
® Wenner, C. A., W. A. Roumillat, J. E. Moran Jr., M. B. Maddox, 
L. B. Daniel III, and J. W. Smith. 1990. Investigations on 
the life history and population dynamics of marine recre¬ 
ational fishes in South Carolina: part 1, 177 p. Mar. Resour. 
Res. Inst., S. C. Wildl. Mar. Res. Dep., Charleston, SC. 
1995; Novakowski et ah, 2008; Zahn Seegert et ah, 
2014)—a finding that indicated food niche segregation. 
For winter and summer flounder of equivalent sizes, 
however, dietary overlap was inversely related to to¬ 
tal length. Moderate to high resource overlap occurred 
among small winter and summer flounder (<40 mm TL) 
and was attributed to their mutual reliance on cope- 
pods and, to a lesser extent, amphipods. Ontogenetic 
dietary shifts exhibited by winter and summer flounder 
then resulted in notable deviations in their food habits, 
although amphipods remained a common prey among 
larger individuals (up to 85 mm TL). 
Multiple species of flatfish often coexist in nursery 
habitats as juveniles (Burke, 1995; Rooper et ah, 2006; 
Nissling et ah, 2007; Mariani et ah, 2011), leading to 
potential interspecific competition (Zloch and Sapota, 
2010). Niche overlap is typically minimized, however, 
because of differences in prey preferences (i.e., biologi¬ 
cal or diet segregation) or fine-scale distribution pat¬ 
terns within the nursery (i.e., physical or spatiotem¬ 
poral segregation), the latter in response to heteroge¬ 
neous environmental conditions (Burke, 1995; Rooper 
et ah, 2006; Mariani et ah, 2011). Moreover, occurrenc¬ 
es of significant dietary overlap of flatfish species do 
not necessarily result in competitive interactions, given 
that the foraging rates of most juvenile flatfish are in¬ 
sufficient to reduce prey abundances to levels that are 
biologically limiting (Kuipers, 1977; Evans, 1983; Shaw 
and Jenkins, 1992). 
In this study, resource partitioning did not occur 
through spatiotemporal segregation, considering that 
-84% of the seine hauls that collected summer floun¬ 
der also yielded winter flounder. Alternatively, the rela¬ 
tively low degree of dietary overlap of flounder species 
was attributed to interspecific differences in prey pref¬ 
erences, and dietary differences were most evident at 
larger body sizes of winter and summer flounder. The 
diet segregation between winter and summer flounder 
may also be explained by differences in their respective 
feeding morphologies. Summer flounder have a rela¬ 
tively large mouth with canine-like teeth (Woolcott et 
ah, 1968), which enables the capturing and processing 
of larger prey items (Manderson et ah, 2000). In con¬ 
trast, the small mouth and reduced gape size of winter 
flounder imposes morphological constraints on their 
diet, which is limited to small-body prey throughout 
their development (Stehlik and Meise, 2000; Vivian et 
ah, 2000). 
This study does provide some evidence of significant 
dietary overlap for small winter and summer fiounder 
(<40 mm TL); yet it is hypothesized that the abundanc¬ 
es of either flounder species did not attain levels where 
interference or exploitative competition could cause the 
limitation of food resources (Evans, 1983; Modin and 
Pihl, 1994; lies and Beverton, 2000; Taylor et ah, 2016). 
Accordingly, the failed recovery of winter flounder in 
southern New England habitats, including the Narra¬ 
gansett Bay and contiguous waters (Collie et ah, 2008; 
NEFSC^), does not appear to be associated with puta¬ 
tive competition with juvenile summer flounder. 
