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Fishery Bulletin 95(3), 1997 
gradient (Fig. 7). They were present in relatively 
large numbers during all months. There were no sig- 
nificant differences in catches of winter flounder 
among months for all study years. 
Depth gradient 
The two species of flounder showed a differential use 
of the three sites that comprised the depth gradient. 
There were also differences in the sizes of flounder 
that used the three sites. Seasonal changes in distri- 
bution were less pronounced than those exhibited 
along the salinity gradient. 
A broad size range of smooth flounder used site 3 
(Fig. 8). However, their abundance dropped off 
sharply after June of each year, as previously dis- 
cussed (Fig. 9). Winter flounder showed few seasonal 
trends in abundance at this station (Fig. 10). Abroad 
size range of juvenile winter flounder was found here. 
A distinct influx of young-of-the-year winter floun- 
der could be seen at site 3 from August through No- 
vember of each year (Fig. 8). 
At site 4, smooth flounder showed little sea- 
sonal change in abundance (Fig. 9), although 
there was a trend for catches to be lowest in 
late summer and early autumn. Length fre- 
quencies differed between site 3 and site 4. At 
site 4, few larger smooth flounder were present 
during any season (Fig. 11), whereas young- 
of-the-year, which were absent from site 3, 
were collected at most times. Abundance of 
winter flounder at site 4 was lowest in all years 
in early summer (Fig. 10), and catches were al- 
ways smaller than those at site 3. Length fre- 
quencies indicated that smaller winter flounder 
made up a greater proportion of the catch at site 
4 (Fig. 11) as compared to site 3 (Fig. 8). 
Catches at site 5 were very variable for both 
species and showed no clear seasonal patterns 
(Figs. 9 and 10). Smooth flounder catches at site 
5 were dominated by young-of-the-year. Few 
larger (>100 mm TL) individuals were ever caught 
at this site (Fig. 12), in contrast to site 3 (Fig. 8) 
but similar to site 4 (Fig. 11). Winter flounder 
occurred at site 5 sporadically and in very low 
numbers (Fig. 10). Catches of winter flounder 
were a mix of different sizes of juveniles. 
Discussion 
A variety of habitats are available to smooth 
and winter flounder in upper Great Bay Estu- 
ary. It was the purpose of this study to quan- 
tify the occurrence of these two species in vari- 
ous habitats. Although the species ranges of 
smooth and winter flounder overlap broadly, 
the evidence presented here indicates that 
they use habitats within the estuaries differ- 
ently and that their habitat use is subject to 
seasonal variations. 
Salinity gradient 
In general, smooth flounder were most abun- 
dant at site 2, the mesohaline river mouth 
