Here is the news release by Prof. Meryem Beklioğlu on the recent fish deaths seen in Eymir Lake: Hürriyet news release  

The news summarizes the findings 25 years of Lake Eymir ecological monitoring concluding the increased population of carps (due to inoculations) triggered the depletion in the lake oxygen concentration together with warming in the air temperatures. 

As a results, oygen sensitive species like pike experienced numerous deaths.