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Fishery Bulletin 111(4) 
within each month and across all months (PRIMER-E, 
Ltd., Plymouth, UK 1 ). The nMDS data were calculated 
as the percentage of diet by weight for each month and 
each species-size-class combination and were log-trans- 
formed before use in the Bray-Curtis index to construct 
the sample similarity matrix. Group-average hierarchi- 
cal clustering was then used to identify those predators 
that had dietary similarities at the 60% level following 
Jaworski and Ragnarsson (2006) and Clarke and War- 
wick (2001). 
Habitat and diet overlap 
Habitat and diet overlap between pairs of species size 
classes were determined through the use of Schoener’s 
index (Schoener 1970). This index was calculated with 
this equation: 
a = l-0.5(x|py-pi^|)» (3) 
i=l 
which shows the overlap (a), where pij and pik are the 
proportions of the ith resource (trawl station or prey 
proportion) used by species j and k, respectively. Index 
values range from 0 to 1, with values >0.6 representing 
biologically important overlap in resource use (Wallace, 
1981; Buckel and McKown, 2002; Bethea et al., 2004). 
Results 
Spatial distribution, abundance, and sizes 
The spatial distribution, abundance, and size distribu- 
tion for each of the 4 predators were variable over the 
course of our 5-month study (Table 1, Figs. 2 and 3). 
Summer Flounder were the most consistently collected 
species throughout this study. They were distributed 
throughout our study area, with a slight shift in abun- 
dance from offshore to inshore in summer followed 
by the reverse in fall. The size distribution of Sum- 
mer Flounder was relatively constant, with individu- 
als of 206-670 mm TL representing a broad range of 
age classes (YOY to 4+) collected from June to Octo- 
ber. Weakfish (80-565 mm TL) also were collected con- 
sistently, with greater abundances occurring inshore. 
Catches of Weakfish in June and July were dominated 
by larger size classes (>200 mm TL), with smaller size 
classes (YOY or 1+, <200 mm TL) becoming abundant 
from August to October. Similarly, Bluefish (55-732 mm 
FL) were most abundant inshore. They were dominat- 
ed by larger size classes (>300 mm FL) in June, with 
smaller size classes (<300 mm FL) becoming abundant 
inshore from July to October. 
Striped Bass, which were typically larger (422-920 
mm FL) than the other 3 species (Fig. 3), were less 
abundant and highly variable in time and space. In 
1 Mention of trade names or commercial companies is for iden- 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
June and August, collections of Striped Bass were lim- 
ited to the northernmost strata of the sample area. No 
Striped Bass were collected in July and September, 
likely because the northern strata were not sampled 
during those months. In October, Striped Bass were 
distributed throughout our study area. In all months in 
which they were collected, they were typically inshore. 
Diet analysis 
Because of limited or zero abundance of some species 
size classes in some months (described previously), 
sampling limitations, and the occurrence of empty 
stomachs, adequate food habit information was not ob- 
tained over all species size classes or months. The rela- 
tive contributions of prey types to the diets for species 
size classes in each month are summarized in Table 2 
(species size classes with insufficient samples sizes to 
be included in subsequent analyses are presented). For 
the groups that were considered adequately sampled 
for diet description (Fig. 4) and, therefore, included in 
the cluster analysis, the cumulative trophic diversity 
curves indicated that sample sizes of 30-40 guts were 
sufficient to characterize the diet in most cases. How- 
ever, for some monthly species size classes (e.g., me- 
dium Weakfish in August and medium Summer Floun- 
der in October) trophic diversity continued to increase 
beyond 40 guts analyzed. 
Size-specific patterns in trophic diversity differed 
across species, with Summer Flounder showing de- 
creased diversity with size in June. In contrast, larg- 
er size classes of Weakfish in August and Bluefish in 
October had more diverse diets than did smaller size 
classes of these species. Overall, diversity of prey 
items increased throughout time in Summer Flounder 
and Striped Bass, and it remained low for small Blue- 
fish. Weakfish diet diversity also was relatively stable 
through the 5-month period of this study, with the ex- 
ception of the high trophic diversity of the medium size 
class of this species in August. 
Cluster analysis separated the size classes for each 
of the 4 species into 3 groups in June at the 60% simi- 
larity level (Fig. 5). The first group consisted of large 
(>400 mm TL) Summer Flounder, which preyed pre- 
dominantly on squids (88.1%) (Table 2). Small and 
medium Summer Flounder formed the second group, 
and medium (201-350 mm TL) Weakfish the third. Al- 
though the second and third groups consumed mostly 
fishes (0-73.3% sand lances [Ammodytes spp.j and 6.1- 
52.9% UID and other fishes), they were separated by 
the amounts of decapod crustaceans (2.1-20.9%) and 
squids (8.3-21.5%) in the former and mysids (33.4%) 
in the latter. 
In July, the cluster analysis identified 3 groups at 
the 60% similarity level from among the 4 species size 
classes for which enough data were available. Small 
and medium Summer Flounder were grouped together, 
with diets consisting of both pelagic and benthic prey, 
including Butterfish ( Peprilus triacanthus ; 15.8-18.7%), 
