Genetic differences between the Chinese and European races of the common carp. II. Multi-character variation-a response to the diverse methods of fish cultivation in Europe and China.

The European and Chinese races of the common carp and their F1 crossbreds were tested in five experimental environments. The two races differ widely and conspicuously in many characters. The Chinese carp has poorer growth rate but higher viability and fertility, earlier sexual maturity, higher resistance to crowding, better adaptation to unfavourable pond conditions, higher seine escapability, longer body and larger weight differences between females and males. The crossbreds between the two races are intermediate in some characters (differences in weight between females and males and seine escapability). In other characters (weight gain, specific adaptation to poor conditions and viability), the crossbreds showed dominance or even heterosis. An hypothesis was advanced to explain these genetic differences in terms of selection response to the different fish-farming practices that existed in the two regions. Specific suggestions were made for implementation of the present findings to genetic improvement of carp breeding stocks.