Diversity and site occupancy of fish communities
Altogether 30 bony fish taxa and one lamprey were identified in the 189
reservoir samples (Table 4, Figure 2). Across the dataset (i.e. all
reservoirs and seasons), no fish were detected in nine pelagic and two
littoral samples. Six taxa were detected in all reservoirs and seasons,
and another 14 taxa were consistently detected in the same reservoir in
summer and autumn. Conversely, six taxa were only detected in one
sampling campaign (Table 4). Seven taxa were categorised as non-native
and others were sorted in six IUCN categories from Extinct, Critically
Endangered, and Vulnerable, to Least Concern (Table 4).
Římov possessed the most taxa whereas Klíčava had the lowest number of
taxa (Figure 3). In all reservoirs, significantly more taxa were
detected in late autumn compared to summer (t2 = 12.124,
p = 0.007) (Figure 3). The Spearman’s rank correlation coefficient
between site occupancy and gillnet score for each taxon was
statistically significant for all sampling campaigns (Figure 5, p ˂
0.05). The rho correlation coefficients were higher in summer than in
late autumn, but this was not statistically significant due to low
sample size (t2 = 1.981, p = 0.186).
More taxa per sample were detected in the main inflows than in the side
tributaries (GLMM: F3,6 = 6.458, p = 0.026) and in the
main reservoirs (GLMM: F3,177 = 11.918, p ˂ 0.001).
Differences in the number of taxa between samples from the reservoirs
and the side tributaries were not significant (GLMM:
F3,177 = 0.327, p = 0.806) (Figure 3). In the main body
of the reservoirs, the number of taxa was significantly different
between localities showing an increasing trend from the dam to the
tributary (GLMM: F3,171 = 14.473, p ˂ 0.001). Moreover,
the in-reservoir habitats differed in the number of taxa with highest
diversity in the littoral zone (GLMM: F12,162 = 2.128, p
= 0.017) and without a significant seasonal effect (GLMM:
F3,171 = 0.946, p = 0.420) (Figure 2, 3). The
Bray–Curtis dissimilarity indices were significantly different between
habitats (GLMM: F5,723 = 21.104, p ˂ 0.001) and seasons
(GLMM: F1,722 = 27.689, p ˂ 0.001) (Figure 4).