Gymnocephalus ambriaelacus Geiger & Schliewen 2010

Distinguished from Gymnocephalus cernua by having smaller angle between the posterior dorsal fin margin and the caudal peduncle (90-110° vs. 113-154°), larger eye diameter (10.2-12.3 % SL vs. 7.9-10.5 % SL) and an irregular pattern of large dorsolateral dark blotches vs. a pattern of small dots. Differs from Gymnocephalus cernua by having a deeper body (26.1-33.6 % SL vs. 20.1-30.7 % SL), longer base of the spinous part of the dorsal fin (36.1-41.9 % SL vs. 28.8-39.6 % SL) and higher mean and modal number of dorsal fin spines (modal 15 vs 14). Diagnosed from Gymnocephalus baloni by the combination of the following characters: larger eye diameter (10.2-12.3 % SL vs. 8.2-10.5 % SL), smaller caudal peduncle depth (7.7-8.9 % SL vs. 7.4-10.1 % SL), higher mean and modal number of pectoral fin rays (15 vs. 13) and a steeper convex dorsal profile of the snout (Ref. 84545).

Dorsal spines (total): 14 - 16; Dorsal soft rays (total): 10 - 12; Analspines: 2; Analsoft rays: 5 - 6

Ripe females were collected in shallow water between 3-5 m depth in May and spawned immediately in captivity (Ref. 84545). Eggs, measuring ~1 mm in diameter, were observed on the bottom and were only weakly adhesive, but some of them were floating (Ref. 84545).

Gymnocephalus ambriaelacus is a species of freshwater ray-finned fish, a ruffe, from the family Percidae which is endemic to Lake Ammersee, in the upper Danube basin in southern Germany. This species can reach a length is 11.7 centimetres (4.6 in) (SL). The species is classified as Critically Endangered as its population is declining following the introduction of the ruffe (Gymnocephalus cernua). Some authorities suggest that this taxon may be synonymous with the Balon's ruffe (G. baloni).