Despite anthropogenic disturbance and moderate climate changes fish density and biomass fluctuated non directionally in a small stream

Quantitative fish sampling, which allows the estimation of the density and standing crop, was conducted annually in October over 23 years in a small lowland stream (Poland), which was initially natural (10 years), and then channelized (13 years). Some climatic variables (temperature and precipitation, measured daily) were available for each year of the study. Neither the state of stream channelization nor the climatic variables were significantly correlated with the total density of fish species (N) and their standing crop (SC) in the stream, during study period. Individually investigated species did not respond positively or negatively to channelization and fluctuations in air temperature and precipitation. This can be important information for managers and scientists who deal with the protection of fish in streams.