Studies on temperature effects during incubation of embryos of sea trout (Salmo trutta L.), vendace (Coregonus albula L.), common whitefish (Coregonus lavaretus L.), pike (Esox lucius L.), ruffe (Gymnocephalus cernuus L.), and rudd (Scardinius erythrophthalmus L.) showed optimal incubation temperatures to produce the highest percentage of newly hatched larvae at the best physical condition, of the highest weight and the highest total length, and carrying the smallest yolk sacs. At temperatures deviating from the optimum, an earlier hatching of much smaller larvae with larger yolk sac was observed. Higher rates of developmental malformations, the lower hatching success rate, and a marked reduction of mobility and activity of the larvae were also observed.

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