R. Billard

Diploid gynogenesis induced by heat shocks after activation with UV-irradiated sperm in common carp

Abstract Diploid gynogenetics of common carp (Cyprinus carpio L.) have been produced by heat shocks applied 3–5 min after insemination with sperm genetically inactivated by UV irradiation. The use of red female (visible recessive marker) confirmed the effectiveness of this irradiation. The minimal temperature inducing second polar body retention is approximately 38°C. The highest percentages of diploid viable fry were observed for water temperature shocks at 39, 39.5 and 40°C lasting 1 min 20 s to 2 min.

Organic fertilization of nursery ponds for pike (Esox lucius)

Abstract Repeated dumping of pig manure (0.5, 1.5, 3.0 t ha −1 week −1 or an equivalent of 2.5, 7.5 and 15 kg dry matter ha −1 day −1 ) leads to an increase in pike fingerling biomass of 70% between ponds receiving the lower and upper rates of fertilization. Survival of larvae is also increased by fertilization, but mainly depends on the initial stocking density. Data on zooplankton density and stomach contents of young pikes show the beneficial effects of manuring on the fishpond biocenosis and may explain the better results obtained when a high rate of manure is added, even when the water temperature is low.