A film about children who help to preserve fish resources in the Don, Volga, Daugava rivers. Part 1 of the Don River Basin. Children swim in a boat, find poachers' nets with a sturgeon with a sensor on its back. The guys communicate with the employees of the Rybnadzor. Children climb onto a research vessel, employees tell them about the devices that track the movement of sturgeons. Daugava river basin. A group of schoolchildren are walking along the river in search of salmon spawning grounds. They climb the dam of the Kegums hydroelectric power station, study the device of a fish passage for the movement of fish through the dam (pos. 273.0 m). Part 2 The Daugava River Basin. Children make a halt on the bank, find an eel that crawls from one river to another. The guys find a salmon nest, take the necessary measurements. The Volga river basin. Children and adults help fry from dry flooded meadows to get into the river. They carry water with fry in buckets, dig a trench. Two boys are holding a banner with the NDP: "WE WILL SAVE LIVE SILVER." A small ship (pos. 247.4 m) is passing by them along the river.