Reproduction efficiency and some characteristics of the spawning grounds of the pink salmon <Emphasis Type="Italic">Oncorhynchus gorbuscha</Emphasis> in the small salmon watercourse in southern Sakhalin

The peculiarities of the distribution of the freshwater ichthyofauna, bottom sediments and conditions at the spawning grounds, and the egg survivability rate of Oncorhynchus gorbuscha were studied in 2003?2012 in a typical salmon river on Sakhalin Island (Goluboi Ruchei brook, Aniva Bay, southern Sakhalin). The sites characterized by the highest survivability rate of the embryos of the pink salmon are inhabited by the freshwater fish community where the juveniles of masu salmon O. masu and whitespotted char Salvelinus leucomaenis dominate. The lengthway bed slope at this site is steeper compared to the sites with lower survivability rates (0.010?0.020 vs. 0.004?0.020?). The maximal positive correlation of the egg survivability rate to the flow velocity of the underflow has been registered for the depth of 30?40 cm, and the maximal negative correlation of the egg survivability rate has been registered to the bottom sediment temperature.