Population of the freshwater amphipod Gammarus fossarum was investigated in a calcareous stream with almost constant temperature (7-8• C) in the Chočské Vrchy Mts (West Carpathians, Slovakia). Quantitative samples of G. fossarum taken during 2005 showed population densities varying from 100 m −2 in August to 585 m −2 in late November. The population was split into juveniles, mature males, mature females without eggs and females with eggs. The percentage of juveniles (40-64%) was always the highest of any of the categories. Ovigerous females occurred throughout the year. The mean sex ratio was 1 : 2.4 (male: female), although its values varied considerably with the time of year. Breeding was continuous, although juvenile recruitment peaked in early spring, summer and early winter. Three discrete cohorts were distinguished from the size frequency distributions. The life span was 6-7 months and the individuals matured approximately in the half of life cycle. The mean fecundity was 9.6 embryos per brood. Variation in fecundity was mostly explained by size of the incubating females. The absolute growth of this species was best described by the Gompertz growth function. Relative growth rates (% body DM day −1 ) fluctuated in a nonlinear manner with size and age. The highest values of daily growth (2-4% of dry mass per day) were noted approximately in the half of life cycle. Annual production, estimated by the size-frequency method, was 1618.9 g dry mass m −2 and P/B ratio was 5.15.

Abstract:The present work gives the result of blackfly fauna research of the Slovenský raj (West Carpathians, Slovakia). Our aim was to describe the composition of blackfly communities, find indicator species for communities, describe environmental factors affecting communities and determine the potential changes in species richness. Research was carried out in 2007 and 2008. The presence of 22 species of blackflies was confirmed at 20 sites in the area of Slovenský raj. 12 species were recorded for the first time in this area. The potential for further increase in diversity was calculated by a nonparametric estimation of species richness. Two main groups of sites with their typical blackflies communities were indentified using a TWINSPAN analysis.