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The invasion of non‐indigenous freshwater fish species is one of the most important threats to aquatic biodiversity. Similar to other Mediterranean countries, Greece is considered a hot spot for freshwater biodiversity, with many range‐restricted endemics of high conservation concern. The aim of this study was to undertake a risk screening assessment to evaluate the invasive potential of non‐native, translocated and traded aquarium fishes in Greece by applying the Fish Invasiveness Screening Kit (FISK). In total, 73 freshwater fish species were evaluated by two assessors. FISK was able to discriminate reliably between invasive and non‐invasive species with a threshold of 15.25. Based on mean scores, 30 species were classified as ‘high risk’, of which 17 as ‘moderately high risk’, six as ‘high risk’ and seven as ‘very high risk’. There was a high coincidence rate for the species categorisation between the two assessors, but significant differences in certainty. The results suggest that FISK is a useful tool for assessing risks posed by non‐native, translocated and traded aquarium fish species in Greece. [ABSTRACT FROM AUTHOR]

In the past, sturgeons were practically unknown in Greece, both to the public and to scientists, the latter not having had the opportunity to study wild populations of the four native species. Populations of stellate sturgeon ( Αcipenser stellatus Pallas, 1771), Adriatic sturgeon ( Acipenser naccarii Bonaparte, 1836), and beluga sturgeon ( Huso huso L., 1758) gradually collapsed by the end of the 1970s. Only the River Evros (Thrace, N.W. Greece) sustained a small fishery and caviar canning operation with European sturgeon ( A. sturio L., 1758) until 1975. Collapse of stocks was mainly attributed to overfishing, pollution and damming. Sturgeons became widely known after initial farming efforts by the Municipal Hatchery at Lake Ioannina in 1992. Broodstock or fertilized eggs of species with high aquaculture potential, such as sterlet ( Acipenser ruthenus L., 1758), Russian sturgeon ( Acipenser gueldenstaedtii Brandt, 1833), bester hybrid ( A. ruthenus × H. huso), paddlefish ( Polyodon spathula Walbaum, 1792), Siberian sturgeon ( Acipenser baerii Brandt, 1869) and white sturgeon ( Acipenser transmontanus Richardson, 1836) were imported into Greece between 1992 and 2004. Hatchery technology, larval rearing and production systems are reviewed in this paper and, despite problems, past and present efforts appear to meet a particular interest of the aquaculture sector as well as of those interested in the restoration of wild stocks. [ABSTRACT FROM AUTHOR]