The article presents the investigation of effect of fluctuations in temperature and content of dissolved oxygen in natural waters and the passage of embryonic and postembryonic development of perch, the study of fish embryos protective response to changes in environmental factors including physiological and biochemical parameters of fish embryos under the influence of abiotic factors aquatic environment.

Fish – primarily water animals that live in the water. Therefore, the properties of water have a significant impact on growth and development and ultimately on the composition of fish fauna reservoirs. Energy supply adaptation mechanisms in fish provided using and disposing of three types of energy-intensive compounds, lipids, protein and glycogen. Unlike most vertebrates in most species of fish protein catabolism of white muscles is widely used in stressful or adverse circumstances as the main source of energy and resynthesis is also used in accordance with the restoration of protein resources for the normalization of living conditions.

Close to adaptability of fish to certain temperature amplitude fluctuation is of great importance at which the same species can live. Usually the fish of tropical and subtropical areas cannot withstand large fluctuations in temperature, unlike fish of moderate and high latitudes.

Research of protein content fluctuations depending on the temperature of incubation was conducted on the native type of fish of our region – European Perch (Perca fluviatilis, L.). As perch spawning occurred in early April so oxygen deficiency in the natural spawning grounds was not observed during the period of research, it was within 4.9–12.3 mg/dm³. The water temperature in ponds varied in the range 8.7–15.8 °С – during incubation of eggs and 16.3–18.1 °С for pre – larva. However, even with these minor fluctuations factors fluctuations in proteins were observed.

At the initial stages of – gastrulation the maximum level of protein in the perch embryos was recorded at 10.4 °С and the minimum temperature at 10.2 °С – 111.4 mg/g, which is 2.5 % less than the maximum. The next stage of development – eye glasses, marked a sharp decline in temperature incubation to 8.7–9.1 °С, with maximum protein content was recorded at a minimum temperature and amounted to – 113.2 mg/g. The minimum value was observed at 9.1 °С (96.2 mg/g), which was less than the maximum value (113.2 mg/g – 8.7 °С) to 15 %. It should be also noted that the difference of temperature between the maximum and minimum data of protein content was only 0.4°С. This shows the great sensitivity of perch embryos at the stage of eye glasses to environment temperature, which we have not seen in the previous stage of development.

For eye pigmentation stage there is a similar trend that was recorded on eye glasses, i.e. with the increasing of temperature protein level decreases. The maximum was seen at 14.9 °С and was 94.9 mg/g, and minimum at 15.8 °С (78 mg/g), which is 17.8 % less.

Research protein content fluctuations continued after the stage of pre-larva. This stage of development is characterized by a significant increase of environmental temperature in the range up to 16.3–18.1 °С. It should be also noted a significant increase in the level of proteins in pre-larva of perch. Throughout the research this figure was within 259.4–323.3 mg/g.

The results of the research found that for the normal development of perch embryos normal temperature range is 9–11 °С, and for the development of pre larva the temperature is within 16 °С.

Key words: European Perch, embryonic development, embryo, pre-larva, water temperature, content of dissolved oxygen, level of proteins.