Level of in vitro storage of the European catfish (Silurus glanis L.) eggs at different temperatures.

Abstract

European catfish (Silurus glanis) is a commercially important freshwater fish originating from Eastern Europe. The objective of this study was to examine the short-term storage of its eggs especially in relation to maintaining a low level of malformation in newly hatched fry. The eggs from freshly spawned individuals were stored separately in cell incubators at 17 and 22 degrees C under aerobic conditions. Changes in fertilization, hatching, and malformation were examined in eggs stored at 1, 3, 5, and 7 h post-stripping. The sperm used for fertilization showed very good motility rates (84-90%) and curvilinear velocity (110-125 mu m/s), and straight-line velocity did not drop below 77 mu m/s. For all females, a temperature of 17 degrees C was better than 22 degrees C for egg storage in vitro. Egg fertilization and total hatching decreased rapidly after 7 h storage at 17 degrees C. The storage time of eggs in vitro to fertilization should therefore not exceed 5 h at 17 degrees C. In all females, there was no difference in the total number of eggs hatching between 1 and 3 h of egg storage at 17 degrees C. The storage time of eggs did not correlate with the level of malformations of the fry. However, the level of hatching and malformations was clearly affected by the storage temperature of eggs when it was > 17 degrees C. Analysis showed that the storage time of eggs, temperature of storage, and individual females had a significant influence on fertilization and total hatching rates. Regression analysis confirmed a low correlation of fertilization and hatching rates with storage time of eggs.