Alien fish species in upper Sakarya River and their distribution

摘要

Sakarya River is one of the most important fishing areas in Turkey. The river provides reproduction and survival areas which are suitable for many fish species by means of both the warm water sources and the wide flood plains. However, the fact that the flood plains have been reclaimed, excessive hunting, destruction of the ecologic balance and invasion of the area by the alien fish species threatens the fish stocks in Sakarya River. In this study, we aimed to determine the dispersion area of?Carassius gibelio?(Bloch, 1782),?Oreochromis niloticus?(Linnaeus, 1758) and?Clarias gariepinus(Burchell, 1822) as the alien fish species. Between years 2005 and 2010, the dispersion areas of these three species in Sakarya River have been determined by means of catching in irregular time periods in the entire Sakarya River. The dispersion details of every of the three species has been yielded with this study for the first time and the natural populations created by?O. niloticus?in Sakarya River was determined for the first time in this study.