Capossela et al Migratory and within-estuary behaviors of adult Paralichthys dentatus of the southern mid-Atlantic Bight 
193 
Table 1 
The total detectable area (km 2 ) that we monitored for the presence of Summer Flounder 
and the percentage of the total detectable area in each defined region (upper channels, 
lower channels, tidal flat, and inlet) of the Wachapreague lagoon system, on the basis of 
a 350-m detection range, for this study of Summer Flounder ( Paralichthys dentatus ) be- 
haviors. Also included are the proportions of time Summer Flounder spent in each region 
and the proportions of fish found in each region over the residency and emigration periods 
(8 June 2007-17 January 2008). The sum of the proportion of fish that used each region 
exceeds 1 because a single fish could occupy more than 1 region over the study period. 
Region 
Detectable 
area (km 2 ) 
Percentage 
of total area (%) 
Total mean 
proportion 
of time (%) 
Total 
proportion 
of fish (%) 
Upper channels 
2.75 
39.2 
78.1 
97.8 
Lower channels 
2.21 
31.5 
19.4 
28.9 
Tidal flat 
1.29 
18.5 
0.4 
4.4 
Inlet 
0.76 
10.8 
2.1 
67.7 
Total area 
7.01 
tistics were calculated to assess the fit of the model 
through the use of the LOGISTIC procedure in SAS. 
Within-estuary behaviors 
We ascertained the temporal and spatial distributions 
of Summer Flounder in the upper channels, lower 
channels, tidal flat, and Wachapreague Inlet by ex- 
amination of monthly distributions of Summer Floun- 
der until all fish finally dispersed. Because the total 
detectable area that we monitored for the presence of 
Summer Flounder varied between regions (Table 1), 
our assessment of fish activity by region did not rely 
on continuous detection. We calculated the proportion 
of fish in each region by month as the number of fish 
detected in a region divided by the total number of fish 
present in the system that month. We also calculated 
the proportion of time the average fish resided within 
a region each month as the total time a fish spent in 
a region divided by the total time spent in all regions 
that month. Time in a region was defined as the total 
time between the first and last detection before de- 
tection in another region; receivers provided sufficient 
coverage to monitor fish movement into and out of the 
4 regions (Fig. IB). For fish that moved between re- 
gions, we did not use the length of time between the 
last region-specific detection and the next region-spe- 
cific detection because we could not objectively assign 
fish location during that interval to a specific region. 
Because not all fish could be assigned objectively to a 
region each month, the sum of the proportions of fish 
using each region could be <1 for a given month. Con- 
versely, the sum of the proportions of fish using each 
region could be >1 because a single fish could occupy 
more than one region in any given month. In addition 
to monthly analyses, we calculated the proportions 
of fish present and time spent in each region for the 
residency and emigration periods. The 2 statistic was 
used to test for differences in the mean proportions 
between the residency and emigration periods (Fleiss, 
1981). All proportions were expressed as percentages. 
We used movement between receivers to calculate 
the activity index, which we defined as the total num- 
ber of times an individual moved between receivers 
during nonconsecutive 6-h periods. We limited the data 
to fish in the upper channels during the residency pe- 
riod because the sample size was highest in this loca- 
tion and during this time (8 June 2007 to 10 October 
2007; see the Results section). For each 6-h period, we 
assigned an activity index value of zero when a fish 
did not move between receivers, and a value of 1 for 
each arrival at a different receiver (adjacent or non- 
adjacent). The activity index was weighted to account 
for variation in distances between receivers (rounded 
to the nearest integer) and summarized weekly for 
individual fish by tidal stage (ebb, slack before ebb, 
flood, and slack before flood) within each time-of-day 
interval (day or night). Day (10:00-16:00) and night 
(22:00-4:00) were restricted to these nonconsecutive 
6-h periods to minimize autocorrelations associated 
with successive observations on the same fish during 
day and night periods (Rogers and White, 2007). We 
also computed mean temperature for each period (tidal 
stage, time of day, and week combination). 
We examined the relationship between activity indi- 
ces and week, time-of-day, tidal stage, and temperature 
with a generalized repeated measures model (GEN- 
MOD procedure in SAS). This equation represents the 
statistical model fitted to the data: 
logUijk) = n + «i + <Sj + r k + y, 
where = the mean activity in week i, time of day j, 
and tidal stage k; 
H = the overall mean activity; 
