Otolith Morphology in Gibel Carp Carassius gibelio and Crucian Carp C. carassius (Cyprinidae)

The morphology of asteriscus, lapillus, and (partly) sagitta is described in gibel and crucian carps from a small natural pond located in Nizhny Novgorod oblast, Russia. The otolith shape analysis was conducted to assess the interspecific differences. A comparison of otolith structure shows that the lapillus is more rounded in the latter species, and the asteriscus length (in anteroposterior direction) is larger than its width (in dorsoventral direction) in gibel carp vs. smaller than its width in crucian carp. Bilateral directional asymmetry is registered for some otolith measurements. The two species are significantly different by six shape indices of the asteriscus and lapillus. A distinct separation between three groups (mainly immature C. gibelio < 70 mm FL , mainly adult C. gibelio > 100 mm FL , and C. carassius 37–86 mm FL ) is observed based on Fourier and wavelet analyses of asteriscus and lapillus shapes. Otolith morphology can be used as an additional diagnostic character for the identification of Carassius species and possible hybrid individuals.