9516

• UCREFRP Catalog Number: 9516
• Author: Granath, W. O. J. and G. W. Esch
• Title: Seasonal Dynamics of Bothriocephalus acheilognathi in Ambient and Thermally Altered Areas of a North Carolina Cooling Reservoir
• USFW Year: 1983
• USFW - Doc Type: Proceedings of the Helminthological Society of Washington
• Copyright Material: YES

216

. PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY

TEMPERATURE (OC)

40
30
20

J

100 ESTIMATED
PREVALENCE (%)

80

60

40

20
o

I:~,~,

M A M J J A SON D J F M A M J J A
1980 1981

I
SON D J F
1982

~I

Figure 5. Monthly changes in temperature, and estimated prevalence and density of Bothrioceph-
alus acheilognathi within Gambusia a./finis from the thermally altered site (HA 1), The horizontal bar
indicates when recruitment occurred.

rriosquitofish (>40 mm) fed primarily on large insects and their larvae during
most of the year, although some copepods were consumed during late summer
and fall. Similar changes in prey consumption by other fish species have been
noted previously (Ball and Kilambi, 1973; Smith, 1973),
The variable foraging patterns of G, affinis may partially explain the seasonal
fluctuations in density and prevalence of B, acheilognathi, Densities of the cestode
in the larger size class were generally lower than in other size classes throughout
the year. Because the former rarely fed on copepods, recruitment probability for
the parasite would be reduced. On the other hand, prevalences of the parasite
were similar among all three size classes, increasing during late summer and fall.
This period coincides with the only time during which copepods formed a sub-
stantial portion of the diet among larger mosquito fish. All parasite recruitment
ceased in late fall and did not resume until the following spring. Although repro-
ductive activity of the fish was continuous at the heated site throughout the year
and could be important (as a dilution factor) in understanding changes in density
and prevalence during the cooler months, reproductive activity was not continuous
in ambient areas, yet prevalence and density still declined, Such changes may be
the result of density-dependent factors, and will be discussed elsewhere (Granath
and Esch, 1983a),
Another factor that could be of significance in influencing the dynamics of B,
acheilognathi in Belews Lake is the seasonal change in abundance of copepod

,