Atherina boyeri Risso, 1810 appeared in the Kuchurgan reservoir-cooler of the Moldavskaya GRES in the early 1980s. Currently, it is the most massive species of fish in the reservoir. Atherina got into the reservoir, most likely together with the pumped water from the river Turunchuk. Due to the high potential of reproduction, as well as eurybiontism, sinter in a short time took a dominant position in terms of numbers in the ichthyocenosis of the Kuchurgan reservoir. Due to the high mineralization and increased thermofication of the reservoir, atherina has found a favorable ecological niche for itself here. According to the dominance index, it belongs to the D5 category, according to the constancy index - C2 and C3, according to the environmental significance index - to the W5 category. The maximum dimensions and weight of males are 9.4 cm and 3.9 g, and females are 9.8 cm and 4.3 g, which is lower in comparison with the marine form.