CHIRONOMID (DIPTERA) LARVAE OF THE BUTONIGA RESERVOIR, ISTRIA, CROATIA, AND ITS FEEDER RIVERS

After the formation of a drinking water reservoir at Butoniga, Istria, research on the fauna of the Chironomidae larvae was undertaken in the feeder waters and the reservoir itself. Forty eight species were identified, belonging to the subfamilies Chironominae, Orthocladiinae, Diamesinae and Tanypodinae. Chironomidae colonized the reservoir waters relatively more quickly than other groups of macroscopic invertebrates. The similarity quotient (QS) of Chironomidae of the feeder waters and the reservoir is only 37.8%, which points to the formation of new communities in the reservoir. There were qualitative and quantitative changes in the composition of Chironomidae fauna in the river Mirna and in the river Butoniga downstream from the dam after water was released from the reservoir for the purpose of testing the dam. The Chironomid composition of the feeder waters places them in quality grade II. In the Butoniga reservoir the bottom water was assigned to grade II-III, because of the decomposition of the remains of surface fauna.