DIGITALNA ARHIVA ŠUMARSKOG LISTA
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| ŠUMARSKI LIST 11-12/2013 str. 42 <-- 42 --> PDF |
phoxinus). In Norrån also pike (Esox lucius) and bullhead (Cottus gobio) occurred (Sjöberg & Hägglund 2011). Samples were taken from five first- to fourth-order streams, with quite different drainage areas and medium year flows (Table 1). The sites where field work was undertaken had to fill certain criteria. First, they should have a beaver dam that raised the water level substantially (Fig. 2B). Streams with small beaver dams raising the water level less than 0.5 m were not considered. The area downstream of the dam had to have a certain minimum water velocity for the functioning of the drift samplers (Fig. 3). To avoid dealing with large lake effects (which would make any possible effects of the dam more difficult to detect), we avoided beaver dams close to lake outlets. The amount of beaver activity was estimated by looking after signs of foraging activity or tracks |