What the heck? On the finding of genus Oncorhynchus Suckley, 1861 individuals at the National Park of Mount Olympus, Greece

The Mediterranean region stands as a prominent biodiversity hotspot for the full spectrum of its habitats. However, it ranks among the most extensively invaded regions globally. This characterization aptly applies to the Balkan Peninsula, an expanse renowned for its elevated levels of biodiversity and endemism concerning freshwater fishes. Among the most frequently introduced fauna in the Balkans is the rainbow trout Oncorhynchus mykiss (Walbaum, 1792). Among the regions with very limited information available concerning the species’ distribution in Greece is Mount Olympus. The current study reports the first record of several Oncorhynchus individuals from upstream of Enipeas River. The specimens in view are the first ichthyofauna record for the region. Also, this manuscript discusses the potential introduction vectors. Two different methodologies were used. The first was the use of citizen-science and the second was the use of underwater cameras and systematic surveys at Enipeas River. The estimated depth at sampling stations ranged from 0.5 to 2 m. Trout individuals were found in all sampling stations, estimated at 7–10 cm in length.