Lake Orhid, located at the border between Albania and the Former Yugoslavian Republic of Macedonia (FYROM), is a lake of outmost ecological importance because of their unique geological and ecological characteristics. It is a hotspot of freshwater biodiversity, it is the habitat for more than 210 endemic species of high economical and cultural value, and it provides many diverse and valuable Ecosystem Services (ESS), as sustainable tourism, food production and supply of freshwater. Among these, the provision of habitat for iconic species is a characteristic ESS. The dynamic of its supporting functions is object of study in the H2020 project ECOPOTENTIAL, that developed a framework, based on the DPSIR approach, for applying the ESS concept for improving the management of Protected Areas (PA). In this study, the evaluation the impact of eutrophication on the survival of the Salmo letnica, an iconic species of the lake, is studied through a simple ecological model.