Morphological recognition of artificial F1 hybrids between three common European cyprinid species: Rutilus rutilus, Blicca bjoerkna and Abramis brama.

The F1 hybrids of roach Rutilus rutilus, silver bream Blicca bjoerkna, and common bream Abramis brama from experimental reciprocal cross-breedings were identified at 18 months of age in relation to the parental species. The morphological analysis, including quantitative (plastic and meristic) and nonmetric features differing in the roach, the silver bream and the common bream, revealed that roach * common bream and roach * silver bream hybrids were easier to distinguish from their parents than silver bream * common bream hybrids. These roach hybrids had many morphological similarities such as the upper iris coloured in red as in the roach, and they were morphologically intermediate to the two parents. This contrasted with the silver bream * common bream hybrids, in which intermediate characteristics were also observed, but with some parental variants. Roach * silver bream hybrids were distinguishable from roach * common bream hybrids by its large eye, its lower scale numbers along the lateral line and its two rows of pharyngeal teeth. Silver bream * common bream hybrids, compared to the two other types of hybrids studied, had higher anal fin soft ray numbers and a clear eye iris with a median black line. In all interspecific crosses of these three cyprinid species fish, the reciprocal hybrids were generally indistinguishable.