DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 11-12/2013 str. 44 <-- 44 --> PDF |
The drift sampler (Fig. 3) was made of a metal tube with an opening diameter of 12 cm, which gave an effective sampling area of 113 cm2. The tapered net had a mesh aperture of 0.5 mm (Elliott 1970). At the back of the net, a 500 ml plastic bottle was fixed with a net at the bottom. The residuals were tested for normality (Shapiro-Wilk W Test) and for equality of variance (O’ Brien test) to see if conditions were met for using Anova. A Two Way Anova test was used for the statistical analysis of all parameters except the functional feeding group ratios, where the residuals were not normally distributed. Drift densities were transformed with the fourth root (Allan & Russek 1985). The Friedman test was used for the functional feeding group ratios and before testing, the data from the three drift traps in each site were combined. Data from Lötbergstjärnbäcken were excluded from the functional feeding group ratios because there were so few individuals in this stream. Results Rezultati Temperature and pH were only measured in the upstream part in every stream. Both pH and temperature were highest in the largest stream, Norrån (Table 3). The bottom substrate and water velocity varied both between different streams, and between the upstream and downstream sampling points (Table 3). A total number of 3882 and 1758 animals were caught in the upstream and downstream parts respectively. In Kroktjärnbäcken, which had the highest catches (Fig. 5), the |