Fig 1.
A map showing the location of the Vír, Vranov and Římov Reservoirs in the Czech Republic (a) and a detailed view of the bathymetric map of the Vír Reservoir (b).
In (b), 0 corresponds to the surface level in late July 2010. The legend shows contour lines with relevant depths. The sampling design of the Vír Reservoir consisted of four sections (Tributary, Upper, Middle and Dam) along its longitudinal gradient.
Fig 2.
Abundance of YOY fish in pelagic water layer of the Vír Reservoir in 2010 and 2011.
Mean abundance of YOY perch (grey colour)and other YOY fish (black colour)according to the fry trawl catches (Number of tows: 63, sampled water volume: 337.413 m3).
Fig 3.
The gut contents of cyprinids from the Vír Reservoir in 2010 and 2011.
The caught cyprinids were: common bream (Abramis brama), common carp (Cyprinus carpio), bleak (Alburnus alburnus) and roach (Rutilus rutilus). No common carp were caught in 2011. The gut content was divided into five categories: YOY fish (dashed), Zooplankton (grey), Insect and Zoobenthos (black), Planktonic Cyanobacteria (white), and Detritus (dotted).
Fig 4.
Comparison of length-weight relationships of common bream (Abramis brama).
Data of 179 individuals with standard length ˃ 260 mm were obtained by sampling from three reservoirs in 2010 and 2011. The comparison was performed by generalized linear model with a log link function. Legend: Vír Reservoir 2010 (designated with dots and solid line, y = 5.864 × e 0.0092), Vír Reservoir 2011 (triangles and dashed line, y = 5.942 × e 0.0090); Vranov Reservoir 2011 (crossed square and dotted line, y = 6.146 × e 0.0086) and Římov Reservoir 2010 (asterisk and dash-dotted line, y = 6.252 × e 0.0071).
Fig 5.
Vertical profile of abundance (horizontal bars for epi-, meta- and hypolimnion) and carapace size (box and whisker plots) of D. longispina cp.
Data were obtained in the dam section of the Vír Reservoir in 2010 for a) June and c) July, and in 2011 for b) June and d) July. Black lines with black dots show the vertical temperature profiles. Box and whiskers plots: median values, upper and lower quartiles (boxes), maximum and minimum values (whiskers), and all outliers (dots) are shown. Arrows with dotted line indicate the minimum carapace size needed for reproduction according to Petrusek et al. [44]. The triangle in the center indicates water transparency measured by Secchi disk.
Table 1.
Mean carapace size (± S.D.), mean abundance (± S.D.) and population percentage share (PPS; i.e., relative Daphnia abundance from the entire water column) of D. longispina complex in the Vír, Římov and Vranov Reservoirs.