Potamon fluviatile crabs' unusual size, up to , and longevity (up to 15 years) are also interpreted as evidence of a long-established population, by analogy with island gigantism. On the island of Malta, "Potamon fluviatile" is rare and restricted to a few locations in the west of the island. On Gozo, there is a single population which inhabits a stretch of river only long. In the Balkan Peninsula, "Potamon fluviatile" is known to occur in Croatia, Montenegro, the Republic of Macedonia, Albania and Greece. There are four species of "Potamon" in the Balkans, and "P. fluviatile" is replaced by "Potamon ibericum" in
Potamon fluviatile are right-handed. In the Tosco-Emilian Apennines, "P. fluviatile" is only found south of the watershed, in contrast with the crayfish "Austropotamobius pallipes", which occurs on both sides on the mountains. Although their ranges overlap, the two species do not inhabit the same water courses, apparently because the crab outcompetes the crayfish, which is therefore forced to live in less favourable locations where the crab cannot survive. Non-indigenous crayfish may pose a greater threat to "P. fluviatile" than native crayfish, although the greatest threats remain pollution, overfishing and the draining of wetlands. The natural range of "Potamon fluviatile" is highly fragmented,