Aquatic Invasive Alien Species in Lake Ohrid: Horizon Scanning and Assessment with Aquatic Species Invasiveness Screening Kit

The study comprises the horizon scanning of the aquatic invasive and alien species (IAS) in the region of Lake Ohrid as a risk assessment area (RA). It included three already established species and their possibility of further spreading (Elodea canadensis, Physella acuta and Lepomis gibbosus) and three IAS present in the surroundings but not yet detected in the region of Lake Ohrid (Eichornia crassipes, Corbicula fluminea and Dikerogammarus villosus). The selection of the potential IAS for assessment has been done based on the following three criteria: an elevated level of invasiveness and impact on a global scale, presence in the geographical proximity (horizon countries) and climate similarity between the horizon area and the RA area. The latest available data point out the positive trend in the distribution of the established species, which, in the last 60 years since its introduction (such as E. canadensis), have increased their distribution along the whole littoral zone of the lake and coastal waters. With the application of Aquatic Species Invasiveness Screening Kit (AS-ISK), all the six species were assessed and their scores of invasiveness were calculated. The results from the screening indicate a high level of invasiveness and impact for all six species, whereby, the highest expected is the impact on the native biodiversity of the RA area. The fact that biodiversity, enhanced endemism and relic species give the Lake Ohrid a status of increased scientific importance, uniqueness and peculiarity, enacting management and eradication measures towards protection from the IAS is more than appealing and urgent.