Changes in the ichthyofauna of Latvia's inland waters and their causes have been analyzed. Information about the distribution and occurrence of fish, obtained from various sources of literature, official reports, "BIOR" data bases on fishery statistics, as well as field research done from 1990 to 2010, has been collected and compared. Anthropogenic activity in the 20th century, such as rivers blocking by dams and fish introduction and acclimatization, has affected ichthyofauna more significantly. Keywords-Latvia, inland fish, changes of ichthyofauna, inland waters I.INTRODUCTION

Occurrence and distribution of fish in rivers of Latvia This publication is a review of data on fish and lamprey species found in 435 of Latvia's rivers and related reservoirs. A total of 43 fish species and three lamprey species, whose life cycles are, at least in part, associated with rivers, have been recorded. These can be divided into freshwater species and diadromous species. Differences between chronologically older publications and records collected since 1990 on fish occurrence are examined. Since 1990, the intensity of study of Latvia's rivers has increased, which is the reason for changes in the conception of the distribution and occurrence of fish species. The authors propose a new fish species list for Latvia's rivers, based on the newest field research and fishery data. The species included in list were caught in research trips during the period 1990 - 2010, or their capture was confirmed by an expert.