In 1975–2005, we utilized data on water quality (N-NH4+, O2, Cl-) and number of carp caught (CC) as environmental data, and sport fishery statistics as species data, fromthree fishing stretches of the Berounka River, Czech Republic. An indirect gradient analysis (DCA) for calculating the strongest gradient affecting the species data, and direct linear gradient analysis (RDA) were used for assessing the relationships among environmental and species data. All RDA models were significant and consecutively explained 45.5, 39.6, and 39.7% of the variability of species data. The strength of environmental variables was evaluated by partial RDA. In the first stretch below the City of Plzeň, with the poor water quality and low carp yields, all environmental variables were significant and the CC data alone explained 26.2% variability of species data. In the second stretch, with intermediate water quality and carps yields, only two environmental variables (O2 and Cl-) were significant and in the third stretch near the city of Prague, with the same water quality and exceptionally high yields, the environmental variables did not significantly influence the species data. These results indicate that sport fishery statistics can be used as at least one source of information for studies of fish assemblages in streams where other data is lacking.
A four-year experiment with a total of 993 individually-tagged barbel, Barbus barbus, resulted in the assessment of survival and abundance. The mean annual survival rate was 0.862, but the partial values assessed separately for seasons (spring – autumn and autumn – spring) differed considerably and the possible reasons for this phenomenon are discussed. On the basis of known survival rate, the abundance was subsequently estimated (for the entire studied stretch and per hectare) using the Petersen capture-recapture method for the period spring 1999 to autumn 2002, and the mean value reached 303 ± 110 ind.ha-1 (minimum 195, maximum 498 ind.ha-1). The Jolly-Seber method was also used to estimate abundance from autumn 1999 to spring 2001 and gave a mean 425 ± 120 ind.ha-1 and a range 233–563 ind.ha1. These results were in autumn 2001 supported by another simultaneously conducted census following the removal method by Zippin (316 ind.ha-1). The abundance showed a significant tendency to increase during the four-year survey, which is in an accordance with the long-term changes observed in the dynamics of the fish community in this stream.