A possible genetic basis for species replacement: preliminary results of interspecific hybridisation between native crucian carp Carassius carassius (L.) and introduced goldfish Carassius auratus (L.)

Reciprocal crosses between non-native goldfish Carassius auratus and native crucian carp Carassius carassius were produced. The F1 hybrids were viable and vigorous, but attempts to produce F2 progenies were not successful, nor were attempts to produce back crosses. The implications of hybridization, with regard to perceived decline in crucian carp numbers, are considered for water bodies in which these species are now sympatric.