Morphometrics of two morphs of sterlet, Acipenser ruthenus L., in the middle course of the Danube River (Serbia)

Two morphs of the sterlet, Acipenser ruthenus, were clearly recorded in two samplings from the middle course of the Danube River in Serbia. The pooled samples comprised 47.9% pointed‐snout morphs and 52.1% blunt‐snout morphs. The most obvious differences were snout shape and length, mainly the differences in the snout area in front of the barbels. In addition to this snout difference, the two morphs also differed with regard to head lengths and the pre‐ocular, pre‐dorsal and post‐dorsal areas. The determination of morphs is not exclusively related to either location or body size as sources of this mode of variability, although it seems that it is easier to detect these in larger size sterlet.