NEW: Annual Report - George Mason University

density of clupeids and Morone sp. occurred in late May, while yellow perch peaked in
early April.
White perch was the most common fish collected in trawls comprising 30% of the total.
Blueback herring (23.2%), channel cat (9.8%), and bay anchovy (9.1%) rounded out the
group of most common species. In an unusual reversal, blueback herring were actually
more common than white perch at both cove trawl sites. Most of the blueback herring
were collected on three sample dates while the white perch were more evenly distributed
through the year.
Banded killifish was the most common species collected at seine sites comprising 44% of
the total catch. Other common species were bay anchovy (12.4%), white perch (6.9%),
and spottail shiner (6.8%). Banded killifish were the most abundant species at all seining
sites and on most sampling dates.
State and federal scientists have collected adult snakeheads this spring in Gunston Cove
at our Station 6 seine site using electrofishing boats and much longer seines. The
smallest was about 5-8 inches longs, but they also caught a large female that seemed
ready to spawn. They asked us to notify them if we get any juveniles or adults. We feel
confident that we can identify them.
Oligochaetes were the most abundant macrobenthic organisms in 2003 with similar
densities observed in both river and cove. Chronomids were a close second in the cove
while amphipods (scuds) and the Asiatic clam Corbicula were subdominant in the river.
Isopods, spherid clams, and gastropods were also present in the river. Small populations
of gastropods and chaoborids (phantom midges) were found in the cove.
B. Water Quality Trends: 1983-2003
To assess long-term trends in water quality, data form 1983 to 2002 were pooled into a
single data file. The, subgroups were selected based on season and station. For water
quality parameters, we focused on summer (June-September) data as this is the most
stable period and often presents the greatest water quality challenges and the highest
biological activity and abundances. We examined the cove and river separately with the
cove represented by Station 7 and the river by Station 9. We tried several methods for
tracking long-term trends, settling on a scatterplot with LOWESS trend line. Each
observation in a particular year is plotted as an open circle on the scatterplot. The
LOWESS (locally weighted sum of squares) line is drawn by a series of linear
regressions moving through the years. The allows the detection of nonlinear patterns such
as cycles and lags which are not easily detected by linear approaches such as linear
regression. We also calculated the Pearson correlation coefficient and performed linear
regression to test for statistical significance of a linear relationship over the entire period
of record (Tables 10 and 11). This was similar to the analysis performed in the 2000 and
2001 reports.
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