| Abstract [eng] |
A big number of dams in Lithuania is blocking free fish migration. For improvement of fish migration, fishways are built but part of them are not productive because before them there are even more dams, which block the way to reach them. That is why there is a need to look at the various methods, to make better solutions for fish migration. The aim of this master thesis is to contribute to the removal priority of fish migration paths’ barriers. Study objects are fish migration paths in Nemunas, Coastal Rivers and Šventoji basins in Lithuanian territory. To reach this aim, at first were analysed various sources of literature, in which are given used methods in foreign countries and Lithuania. According to it, several specified criteria are used to determine removal priority of fish migration paths’ barriers: ecological condition of rivers, ecologically and culturally important rivers and protected areas (such as ichthyological reserves and NATURA 2000 Habitats Directive areas). As well, more dams are identified, which are not registered in Cadastre of rivers, lakes and ponds. For that, data analysis and statistical methods are used, as well as satellite view and topographic map. Afterwards, there is an evaluation of fish migration paths’ barriers impact in the study area using spatial proximity analysis method. Fish migration is divided into three types – open, limited and closed. The impact on fish migration is evaluated in all rivers and ecologically and culturally important rivers or its parts in the study area. However, the biggest focus is on ecologically and culturally important rivers and identified dams, which block these rivers for free fish migration. These rivers are the most important for fish migration in Lithuania, that is why it aims to open closed migration ways in these rivers. Especially these identified dams are included in the list of fish migration paths’ barriers removal priority and provided recommendations, what to do which these identified dams. Spatial overlay and proximity analysis methods, mathematical and logical methods are used for priority determination. It is determined, what distance would be opened in all rivers, ecologically and culturally important rivers and in protected areas, if identified barriers were removed. That is how the potential fish migration paths’ barriers impact is evaluated. The results reveal, that removal of identified barriers would improve fish migration in Lithuania. |
