Aphanius transgrediens

**Aci Göl Killifish (Aphanius transgrediens)** The Aci Göl killifish is a small freshwater fish endemic to Turkey, measuring approximately 4-6 centimeters in length. Like other members of the Aphanius genus, it displays sexual dimorphism, with males typically exhibiting more vibrant coloration and distinctive vertical bars along their bodies. These fish are opportunistic feeders, consuming small invertebrates, algae, and organic detritus, playing a role in nutrient cycling within their aquatic ecosystem. This species is found exclusively in the Aci Göl (Bitter Lake) system in south-central Turkey, inhabiting shallow, alkaline waters with high salinity levels. The lake's unique hydrochemistry has shaped the evolution of this endemic population, which has adapted to conditions that would be inhospitable to most freshwater fish species. The primary threat to A. transgrediens stems from habitat degradation and water level fluctuations in Aci Göl. Agricultural water extraction for irrigation has significantly reduced lake levels, concentrating salts and altering the delicate chemical balance the species requires. Additionally, pollution from agricultural runoff introduces pesticides and fertilizers that further compromise water quality. Limited conservation measures are currently in place for this critically endangered species. Turkish researchers have conducted preliminary population assessments and habitat monitoring, but comprehensive conservation planning remains underdeveloped. The species' extremely restricted range makes it particularly vulnerable to local environmental changes. The outlook for the Aci Göl killifish remains precarious. Without immediate intervention to address water extraction and pollution issues, this endemic species faces a high risk of extinction in the near future.