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<br />OF WASHINGTON, VOLUME 50, NUMBER 2, JULY 1983 .
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<br />215
<br />
<br />Table 4, Mean density of Bothriocephalus acheilognathi from three size classes of mosquitofish
<br />collected from the thermally altered site (HA 1) from March 1981 to March 1982. (Each mean is
<br />based on N = 20 unless otherwise noted.)
<br />
<br /> Size class (mm) (x I SE)t
<br /> Date ,;30 3]-40 ~41 F:j: (df ~ 2,57)
<br /> 3/81 1.3 :t 0, 6 3,6 :t 0,9 1.8 :t 0.4 6,10*
<br />" 4/81 0,5 :t 0,2 1.6 :t 0,6 1.5 :t 0,5 5,21"'
<br /> 4/81 0,7 :t 0.4 O,9,:!: 0,3 2,5 :t 0,6 6,17*
<br /> 5/81 1.0 :t 0,3 1.9 :t 0,5 1.8 :t 0,5 0,98"'
<br /> 5/81 1.8 :t 0,5 2,l:t 0,5 1.1 :t 0.4 1.1 7"'
<br /> 6/81 1.0 :t 0,3 l,5:t 0,6 4,1 :t 1.2 7,51*
<br /> 6/81 0.4 :t 0,2 1.1:t 0.4 l.7:t1.3 5,03"'
<br /> 7/81 O,2:t 0,1 O,8,:t 0,3 2,0 :t 1.0 5,12"'
<br /> 7/81 0,3 :t 0,3 O,3:t 0,2 0,2 :t 0,1 0,08"'
<br /> 8/81 0,6 :t 0.4 0,5 ::t 0,3 0,6 :t 0,5 0,03"'
<br /> 8/81 0,8 :t 0,7 O,3:t 0,2 ~O,2 :t 0,1 0,16"'
<br /> 9/81 0,3 :t 0,3 l,O::t 0,6 0,6 :t 0.4 1.01 "'
<br /> 9/81 0.4 :t 0,3 0,7 ::t 0.4 0.4 :t 0,2 1,00"'
<br /> 10/81 0,6 :t 0.4 1.0 ::t 0,5 0,6 :t 0,3 1.12"'
<br /> 10/81 4,3 :t 1.3 4,3 ::t 1,0 2,1 :t 0,5 3,68"'
<br /> il/81 5,2 :t 1.0 5,7 ::t 1.9 2,9 :t 1.1 7,38*
<br /> 11/81 5,5 :t 1.0 4,2::t 0,9 2,8 :t 0,5 8.42*
<br /> 12/81 4,8 :t 1.6 5,2 ::t 1.3 3.4:tO,7 5,96*
<br /> 12/81 4.4 :t 1.0 5,0 ::t 1.6 2,7 :t 0.4 9,01*
<br /> 1/82 3,5 :t 1.0 4,2 ::t 1.1 2.4 :t 0.4 5,24"'
<br /> 1/82 3,2 :t 1.1 4,5 ::t 1.1 2,8 :t 0,6 5.41n'
<br /> 2/82 2,9 :t 1.0 4,1 ::t 0,7 2.4 :t 0,5 6,12*
<br /> 2/82 2,1 :t 0,8 2,8 ::t 0,7 2,1 :t 0,5 1.05"'
<br /> 3/82 1.5 :t 0,8 2,6 ::t 0,7 1.8 :t 0.4 2,13"'
<br />F( df) 7,97* 7,64* 6,04*
<br /> (23,456) (23,456) (23,441 )
<br />t Underscored means are not significantly different as determined by Duncan's multiple range test.
<br />:j: * = significant at P < 0.005. nS = not significant at P > 0.005.
<br />S Entry based on N ~ 6, df ~ 2,43,
<br />
<br />It was initially assumed that prey preference of mosquitofi.sh was similar among
<br />all size classes, but this assumption was erroneous. Riggs (pers, comm.), in his
<br />study on the diet of G, affinis in Belews Lake, found that large fi.sh (>40 mm) fed
<br />primarily on dipterans and rarely on copepods, Smaller fi.sh fed mainly on small
<br />insects and copepods, Similar changes in the diet of fi.sh with increasing body size
<br />have been observed for other species as well (Werner, 1974; Keast, 1980). Lowest
<br />densities of the cestode were most commonly seen in the largest size class, and
<br />thus may be related to variation in dietary preference as the host increases in size,
<br />Seasonal changes in the diet of mosquitofi.sh were also noted by Riggs (pers,
<br />comm,). The two smaller groups (::;40 mm) consumed insect larvae and copepods
<br />during the warmer months and only insects during the cooler months. Larger
<br />
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