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

OF WASHINGTON, VOLUME 50, NUMBER 2, JULY 1983 .

213

WATER TEMPERATURE (oG)

I

40
30
20

10

\.

100 PREVALENCE (%)
80

60

40

20

o

12

X DENSITY

~ 30 mm -
31 -40 mm .....
,40mm---

8

4

o

M A M J J A SON D J F M AM J J A SON D J F M
1980 198 I 1982

Figure 4. Hi-weekly changes in temperature, and prevalence and density of Bothriocephalus
acheilognathi within three size classes of Gambusia affinis from the thermally altered site (HA 1).
The horizontal bar indicates when recruitment occurred.

prevalence of the cestode at higher temperatures may be attributed to a dilution
effect created by the addition of uninfected individuals into an expanding host
population. Because of continuous reproductive activity by G, affinis during the
winter at the heated station and the absence of parasite recruitment, the dilution
effect is especially obvious in smaller size classes of fish.
The patterns of parasite recruitment by G, affinis in ambient and thermally
altered areas of Belews Lake are somewhat similar to those observed by Aho et
al. (1982) for Diplostomulum scheuringi in Par Pond, a South Carolina cooling
reservoir. In the heated locations of Par Pond, recruitment of D. scheuringi by
G, affinis began earlier, lasted longer, and was interrupted in the summer for a
period of several weeks when water temperatures rose above 40oC. The same
pattern of recruitment was observed for B. acheilognathi in Belews Lake. The
interruption in Belews Lake, however, corresponded with a period of sharp decline
in prevalence and density of B, acheilognathi, especially in the heated location,
There was also massive mortality among G, affinis at the heated station during
the same time, which would contribute to decreases in density and prevalence.
Mortality of mosquito fish in the ambient areas of Belews Lake was not observed.
Other factors, presumably of a density-dependent nature, are believed to be in-
volved in keeping densities low during the period when active recruitment is
taking place (Granath and Esch, 1983a, b).