Table 3 Mean abundance (±SE) of I. variegatus and I. pileatus in three age cohorts of perch using data from 10% of the fish individuals most heavily infected with each of the parasite species

Cohort

Parasite

n

I. variegatus

I. pileatus

Ratio

t

d.f.

P

0+

I. variegatus

10

6.3 ± 0.7

2.2 ± 1.0

2.86

3.029

9

0.014

I. pileatus

10

25.3 ± 6.9

68.8 ± 8.1

2.72

5.413

9

<0.001

1+

I. variegatus

12

19.1 ± 2.6

5.4 ± 3.3

3.52

6.396

11

<0.001

I. pileatus

12

59.3 ± 15.5

133.2 ± 7.8

2.25

7.358

11

<0.001

2+

I. variegatus

16

28.2 ± 2.2

10.7 ± 2.0

2.64

6.108

15

<0.001

I. pileatus

16

135.1 ± 20.3

293.4 ± 14.4

2.17

5.711

15

<0.001