Table 2
Differences in perch diet composition between the three study periods. N = number of perch with a specific food component; ΣW = total weight of specific food component; Pr(>|z|) = level of significance (generalised linear model), * = p < 0.05, *** = p < 0.001; na = not applicable. Native fish were cyprinids (1981/1982 and 2011/2012) and cyprinids + juvenile perch (1998).
| Food item | 1981/1982 | 1981/1982 vs. 1998 | 1998 | 1981/1982 vs. 2011/2012 | 2011/2012 | 1998 vs. 2011/2012 | |||
|---|---|---|---|---|---|---|---|---|---|
| N | W | Pr(>|z|) | N | W | Pr(>|z|) | N | W | Pr(>|z|) | |
| Zooplankton | 51 | 2.08 | 0.951 | 28 | 2.68 | *** | 65 | 5.95 | *** |
| Chironomid larvae | 107 | 4.82 | 0.314 | 54 | 9.57 | * | 58 | 4.58 | 0.354 |
| Other invertebrates | 26 | 2.99 | 0.086 | 27 | 2.94 | 0.113 | 31 | 9.64 | 0.840 |
| Native fish | 3 | 0.97 | *** | 18 | 3.29 | 0.354 | 4 | 2.33 | *** |
| Tubenose goby | – | – | – | 10 | 8.35 | na | 6 | 18.02 | 0.155 |
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