See:
https://phys.org/news/2019-01-insigh...theastern.html

"The Iron Gates is a unique landscape on the border between modern-day Romania and Serbia where the Danube cuts through the junction of the Balkan and Carpathian mountain chains. It provided a rich wild aquatic resource base for prehistoric hunter-fisher-foragers during the Late Glacial and early Holocene.As farming spread from south west Asia into Europe, prehistoric diets ultimately transformed towards a diet based upon domesticated plants and animals. However, in this region, evidence has suggested that wild resources may have continued to be important well into the early Neolithic.
This research involved analysis of organic residues surviving in the fabric of 8,000-year-old Neolithic pottery excavated from sites on the banks of the Danube.
Chemical analyses allowed scientists to directly see what kinds of resources were being prepared in these newly-appearing pots and compare this with the way the same type of pottery was being used by farmers in the wider Balkans region."

"It is possible that farmers were attracted to this location by the impressive aquatic resources available including huge sturgeon which swam up the river from the Black Sea.It may also be that Late Mesolithic dietary practices are continuing here, but now using new Neolithic pottery as a result of these early interactions between Mesolithic and Neolithic communities."