Genetic differences between the Chinese and European races of common carp

Summary Common carp of the Chinese and European races and their cross were tested in different environments. The test groups were either stocked together into the same pond, or each group was stocked separately. Mean growth, taken as a measure of the quality of the environment, varied widely between treatments. Genotype-environment interactions were estimated by the regression of growth of different genetic groups on this measure of environment. Proportional growth differences between the European and European X Chinese crossbreds, were several times higher in manured ponds than in ponds with artificial feed. The Chinese fish showed the fastest relative growth in poor conditions, with manure as the major nutrient input, while the European fish showed the fastest relative growth under improved conditions and irrespective of its source of food. The Chinese X European crossbred is heterotic over a range of intermediate conditions with manure as the principal nutrient.