The paper aims to identify distribution patterns of Caspian sprats (the main commercial fish in the Caspian Sea) in the epipelagic zone of the Central Caspian Sea in summer and to assess the relationship between the fish aggregation density and the temperature gradient, based on hydroacoustic and hydrological data for 2014–2021. Hydroacoustic surveying was carried out in the deep sea (depth up to 800 m) using a Simrad EK-60 hydroacoustic complex installed on R/V Caspian Explorer with stationary split-beam antennas operating at frequencies of 38 and 120 kHz. Biomass was calculated for standard 10-metre layers from 0 to 50 m. The water temperature was measured at depths of 10, 20, 25, 30 and 50 m. The vertical temperature gradient was calculated for the 20–30 m layer. The relationship between the aggregation density and the gradient was assessed using linear regression analysis. It was found that in summer, the bulk of Caspian sprats, migrating for feeding, concentrates in the middle part of the Caspian Sea, in the upper 50-metre layer. From the results of the 2021 summer hydroacoustic survey, a map of the sprat distribution in the middle part of the Caspian Sea was constructed. The maximum concentrations of sprats were observed in the 20–30 m layer. A significant linear relationship (R² = 0.802) was found between the density of sprat aggregations (over 30 t/mile²) and the vertical temperature gradient in this layer. It was shown that dense commercial aggregations form at a gradient of no less than 0.3 °C/m and a temperature above 9.0°C at a depth of 30 m. The results can be used to estimate the location of commercial sprat aggregations in the deep-water part of the Central Caspian Sea in summer.