Development of Fish Based Index for Assessing Ecological Status of Bulgarian Rivers (BRI)

ABSTRACT

An index has been elaborated to define the ecological status of rivers in Bulgaria, using the fish as indicator for human impact. The index is based on classical approach for biological integrity, employing nine biotic variables and more than 70 freshwater fish species. The main purpose is intended to determine ecological status of Bulgarian rivers according the requirements of the EU Water Framework Directive. The method is fast, simplified and adapted to fishing methods that do not require colecting of specimens. The advantages are that BRI has been especially elaborated for Bulgarian rivers and its sensitivity directed to indication of antropogenic pressures to which the other biological elements are not so sensitive. The methods of the index elaboration have been explained and hints for its practical implementation given.

Keywords:

• biotic index
• fish
• ecological status
• rivers
• Bulgaria