416 
Fishery Bulletin 95(3), 1997 
Site 1 (low salinity, Squamscott River at Route 51), 
site 2 (medium salinity, Squamscott River at Route 
108), and site 3 (high salinity, middle of Great Bay) 
were located along a salinity gradient formed by 
Great Bay Estuary and one of its major tributaries 
(Fig. 1). The mean salinity value at each site varied 
considerably on a seasonal basis, but a salinity gra- 
dient always persisted along these sites. Table 1 sum- 
marizes some physical characteristics of these loca- 
tions. Site 1 was located in the Squamscott River 
about 4 km above the mouth. Although the river is 
still tidal in this area, the water is often fresh or ex- 
tremely low in salinity. Site 2 is also located in the 
Squamscott River but only 0.5 km above the mouth. 
Salinity at this site is highly variable but intermedi- 
ate between the other two sites. Site 3, the site with 
greatest salinity, was located in the middle of Great 
Bay proper. The depth and bottom substratum were 
similar at all three stations (Table 1). 
Sites 3 and 4 (high salinity, shallow Great Bay) 
and site 5 (high salinity, Great Bay intertidal flats) 
were located along a depth gradient in a contiguous 
area in the middle of Great Bay. Site 3 was the deep- 
est site sampled along the depth gradient. Site 4 rep- 
resented the intermediate depth, and site 5 was lo- 
cated on intertidal mudflats and therefore sampled 
only on high tides. All three sites had similar bottom 
substratum, silty mud, and owing to their proxim- 
ity, experienced nearly identical salinities (Table 1). 
Monthly length frequencies at each site were 
pooled over all study years. The Kolmogorov-Smirnov 
test was used to test for differences in length-fre- 
quency distributions among sites. One-way analysis 
of variance (ANOVA) was used to test for significant 
differences in catches among the three sites that 
made up each of the two gradients. To reduce the 
number of ANOVA’s performed and to increase the 
power of the tests by increasing sample sizes, the 
monthly data were grouped into three seasons: 
spring, summer, and autumn. Months of April, May, 
and June were considered spring; July and August 
were considered summer; and September, October, 
and November were considered autumn. Because 
many months contained zero catches and, in some 
cases, the variances were proportionate to the means, 
the data were transformed by using a square-root 
transformation (square root(X+l)). The Kolmogorov- 
Smirnov test with the Lilliefors modification and 
probability plots of residuals indicated no significant 
deviations from normality, and Levene’s test indi- 
cated homogeneity of variances after the transfor- 
mation. Where a significant difference in catches was 
detected among sites, the sites were compared by us- 
ing Tukey’s HSD test (Zar, 1984). 
Results 
A total of 8,333 smooth flounder and 2,105 winter 
flounder were captured during the study period. Both 
juvenile and adult smooth flounder were abundant 
in the study area in contrast to winter flounder, which 
were abundant only as juveniles. However, length 
frequencies of the two flounders were similar because 
adult smooth flounder are about the same size as 
juvenile winter flounder. Smooth flounder were cap- 
tured from many different year classes, whereas win- 
ter flounder were primarily age 0 + , 1 + , and 2 + , based 
on length frequencies. 
Salinity followed a typical boreal estuarine sea- 
sonal pattern (Figs. 2 and 3). The general trend at 
all stations was for salinity to be lowest in April, to 
increase over the late spring and summer months 
reaching the highest levels during August and Sep- 
tember, and to decline during autumn. These sea- 
sonal patterns were especially pronounced at site 1 
and site 2. Salinities in spring of 1991 were higher 
at all sites than in the other two years, a result of an 
uncharacteristically dry spring and limited spring 
runoff. Another salinity anomaly occurring in 1991 
Table 1 
Physical characteristics of the sampling sites. Sites 1, 2, and 3 make up the salinity gradient, whereas sites 4, 5, and 3 form the 
depth gradient. 
Site number 
and habitat 
type 
Salinity (ppt) 
Temperature (°C) 
Depth (m) 
Bottom type 
Mean 
Range 
Mean 
Range 
Mean 
Range 
1 (low salinity) 
4.2 
0.0-22.4 
19.4 
4.7-25.7 
2.7 
1. 9-4.0 
silty mud 
2 (medium salinity) 
10.9 
0.4-24.0 
17.1 
0.0-27.8 
3.7 
1.8-4. 3 
silty mud 
3 (high salinity, greatest depth) 
20.3 
6.5-29.9 
15.4 
1.8-23.9 
6.2 
4. 9-7. 9 
silty mud 
4 (intermediate depth) 
20.9 
6.5-29.5 
16.4 
2.3-24.9 
2.1 
1.5-4. 4 
silty mud 
5 (intertidal flats) 
19.8 
11.0-28.5 
15.2 
0.2-24.2 
1.5 
1. 1-2.2 
silty mud 
