Development of abundance and size structure of young-of-the-year perch populations using three methods

Pelagic underyearling communities in a canyon-shaped reservoir in late summer

“…During early spring, shortly after hatching, percids dominated the open water area of the Římov Reservoir (Matěna 1995), and the same pattern has also been observed in other European lakes and reservoirs too (Wanzenböck et al 1997;Tischler et al 2000;Čech et al 2005;Scharf et al 2009). But what are the species composition and fry densities in late summer?…”

The influence of the trawl mouth opening size and net colour on catch efficiency during sampling of early fish stages

“…During the day inŘímov Reservoir in mid-May, perch dominated the trawl catches in the open water area, whereas cyprinids dominated 2 weeks later. Mid-May has been described as the period with the highest density of perch fry in the open water area of this Reservoir in previous years (Matěna, 1995) and in early spring perch is also the most abundant species in other European lakes and reservoirs (Wanzenböck et al, 1997;Tischler et al, 2000;Čech et al, 2005;Scharf et al, 2009). The dominance of perch in May in the open water is not surprising, because soon after hatching the perch larvae migrate from the littoral into pelagic habitat, and before they return to littoral areas after metamorphosis, the fry stay in the epilimnion for a month or even longer (Ward and Robinson, 1974;Coles, 1981;Treasurer, 1988).…”

“…Another typical characteristic of most studies describing ichthyoplankton densities in lakes and reservoirs is the absence of information about the net colour. In some studies, dark entrances to the main cylinders of the nets (Scharf et al, 2009) or transparent samplers (Noble, 1970) were used, but generally, the potential influence of the net colour on its efficiency has been overlooked.…”

Impact des coupes forestières sur l'écologie des jeunes stades de vie chez la perchaude (Perca flavescens) :

“…early in the season, yellow perch hatch in the littoral zone and undergo a migration to the pelagic zone until it reaches approximately 25 mm long, and then retum to the littoral zone (Whiteside et al 1985, Post & McQueen 1988. Given these size-specific migrations, we used a sampling design in order to have a complete collection of all size-classes as suggested by Scharf et al (2009). During the early July survey, fish were sampled at six pelagic and six littoral stations to catch larvae and/or early juveniles.…”

“…Given these size-specific migrations, we used a sampling design to have a complete collection of all size-classes as suggested by Scharf et al (2009). Sampling sites were randomly located within each survey.…”