BALIK BARİYERLERİNE BİR ÖRNEK: BÜYÜKÇEKMECE BARAJI (İSTANBUL)

Abstract

<div><!--block-->Fish migrations are affected negatively from dams, hydroelectric power plants and some structures built on streams and so, several fish species are under threat of extinction. Species compositions also shows a rapid alteration in their habitats where environmental conditions were changed. Büyükçekmece Reservoir is an example for this case. The lagoon that was blocked from the sea connection in 1985, became a freshwater lake in time and fish composition has changed rapidly. Nowadays, freshwater fish species such as Rutilus rutilus (L., 1758) and Alburnus istanbulensis Battalgil, 1941 took over the marine species i.e. Pomatomus saltatrix (L., 1766) and Engraulis encrasicolus (Linnaeus, 1758). The presence of Atherina boyeri Risso 1810, that was recorded for the first time in the lagoon in 1982, was not reported in a study carried out to determine fish fauna of the reservoir in 1999 (after building of the dam). It was argued that low water temperature has adverse effect on feeding of the species and also caused to its death. However, this species was found in the stomach contents of two Perca fluviatilis L., in 1758 surprisingly, although the lack of sand smelt in the reservoir in a study conducted in 2009. In another study which carried out in this reservoir in 2015, the species was represented by a high number of individuals. It is thought that this species enters into the reservoir and rebuild the population with the opening of the dam shutters in excessive rainy periods. Büyükçekmece Reservoir is an example that influence of the dam shutters on the change in species composition and blocking of fish migrations.</div>