Fish assemblages in lakes along environmental gradients at the eastern edge of Europe

Fish assemblages and environmental variables were studied in 155 lake and pond sites on the east edge of Europe (Tatarstan Republic). The main aim of the work was to describe and identify patterns of fish distribution in lakes from a poorly studied region of Europe. The impact of environmental factors on fish species and communities was analyzed with regression and ordination methods. Fish assemblages, probability of occurrences, and abundance of many fish species were very different between our results at the eastern edge of Europe and those reported from further west in the continent. The size (area) of lakes was the main environmental variable (positively) influencing total abundance, the total number of fish species, and the Shannon diversity index. The probability of occurrence of more than half of the fish species was related to the area and bottom substrate, either on its own or in combination with elevation and water depth. For the first time at this eastern edge of Europe, means and standard deviations for fish species along basic environmental gradients were estimated. The latter were highly variable between species.