About Scardinius hesperidicus Bonaparte, 1845
Scardinius hesperidicus Bonaparte, 1845 can be distinguished from other Mediterranean rudd species by a set of consistent morphological features. It has 36 to 39 scales along the lateral line, 10 to 12+1⁄2 branched fin rays on the anal fin, and 10 to 13 gill rakers. The dorsal profile of its head is straight or slightly convex, with the forward-pointing snout tip sitting at or slightly above the middle of the eye. There is no hump behind the eye, and the eye does not sit close to the head's dorsal profile when viewed from the side. The lower jaw articulates in front of the eye. Head length equals 24–27% of the species' standard length, while body depth equals 35–39% of the standard length. All fins are dark grey in adult individuals with a standard length over 10 cm (3.9 in). The maximum recorded standard length for this species is 40 cm (16 in).
This fish is endemic to the northern Adriatic Sea drainage basin, where its range extends from the Isonzo in Friuli-Venezia Giulia south to the Vomano in Abruzzo. It also occurs in rivers that drain into the Ligurian and Tyrrhenian Seas, specifically within the Arno, Ombrone, Tiber and Volturno drainages, though it is possible that Scardinius hesperidicus was introduced to these systems. It has additionally been introduced to a number of subalpine lakes in France and Switzerland. It inhabits slow-moving or still waters in rivers, and readily colonizes drainage channels, canals, and reservoirs.
