Effect of genetics and temperature on carp juvenile survival in ponds of the temperate climat

In a temperate climate the survival of carp larvae is limited by the pronounced cooling that usually occurs in the period of early stages of larval development, i.e. during the late spring. On the basis of previously obtained results it was assumed that years favourable for the survival of juvenile carp occur when the water temperature in the pond decreases from about 20 °C to about 14 °C more than 10 days after pond stocking. The unfavourable years are those with a temperature decrease occurring earlier. In a shallow nursery pond the cooling causes severe temperature drops that can create lethal conditions for the carp larvae. The frequent temperature decreases encouraged the seeking of carp strains and crossbreeds resistant to such changes. Polish, Hungarian, and French strains and also crossbreeds between them were considered. Under favourable thermal conditions the crossbreeds and strains showed distinctly higher average survival (p = 0.086). In each year the survival rate of the crossbreeds was higher (p = 0.013) although there was a pronounced variability in the survival rate of all breeds and crosses.