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

208

. PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY

the plankton, four fish from each group were killed and necropsied to determine
if they had acquired infections of B. acheilognathi, After 2 wk, the remaining fish
were similarly examined.
DATA ANALYSIS: The Statistical Analysis System (SAS) (Goodnight and Barr,
1971) at TUCC (Triangle Universities Computation Center) was used for the
following tests. Contingency chi-square analysis (procedure = FREQ) was per-
formed on prevalence of the cestode among size classes and between sites. Data
collected on parasite density were converted to ranks, and a one-way analysis of
variance was performed (procedure = NPARIWAY; Kruskal-Wallis test); ranks
were assigned to the number of worms in each fish. Duncan's multiple range test
was performed to determine whether significant differences existed among mean
densities of the parasite in the three size classes of fish.
DEFINITIONS: Prevalence refers to the percentage of hosts infected with B,
acheilognathi in a given sample. Mean density refers to the number of worms
counted in a given sample, divided by the total number (both infected and un-
infected) of fish within the sample, Mean infrapopulation density refers to the
number of worms counted in a given sample, divided by the number of infected
fish within the sample.

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Results

Temperature

A normal seasonal change in surface water temperature occurred over the 2-yr
study period at the ambient study site (M 1) in Belews Lake (Fig, 2). Minimum
temperatures (10oC) were observed in late January-early February 1981 and 1982,
and maxima (32-330C) occurred during August 1980 and June-July 1981.
Water temperatures at the thermally altered site (HA 1) also fluctuated season-
ally, but, in contrast to the ambient site, never dropped below 190C in winter
(December, January, and February) (Fig. 4). During mid- to late summer (summer
includes June, July, and August) of both years, temperatures reached 40oC.

Seasonal dynamics of B. acheilognathi at the ambient station

Recruitment, prevalence, and density of B. acheilognathi in mosquitofish ex-
hibited seasonal cycles at M 1 (Fig, 2). In both years, recruitment began in early
June and continued into October. This pattern is also reflected by the almost
steady increase in prevalence within all three size classes during the summer
months and early fall of 1980 and 1981, Contingency chi-square analysis revealed
a significant variation in prevalence among months (for ~30-mm size class in
1980, x2 = 154.0 with 23 df, P < 0.005; for 31-40-mm size class in 1980, x2 =
116,8, P < 0,005; for >40-mm size class in 1980, x2 = 88.4, P < 0.005; for ~30-
mm size class in 1981, x2 = 104.9, P < 0,005; for 31-40-mm size class in 1981,
x2 = 84.8, P < 0.005; for >40-mm size class in 1981, x2 = 63.7, P < 0.005);
there was no significant difference between years at site M 1 (x2 = 62.3, df= 71,
P > 0.05), The same analysis also indicated that prevalence among size classes
varied significantly only during March and April in 1980,
Mean densities of B, acheilognathi changed in a manner similar to seasonal
changes in prevalence (Fig. 2). Lowest densities occurred in the summer months
of both years in all three size classes of moquitofish, with peaks in early winter.

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