Regularities of reproduction for pink salmon Oncorhynchus gorbuscha from the Iska River

Reasons for rapid rise of pink salmon landings in the Sakhalin Bay (Okhotsk Sea) in the early 21 century are analyzed. Dependence of its juveniles and adults numbers on the number of their parents is well described with Ricker equation, and the recruitment depends linearly on the number of juveniles in the river. Several factors of the pink salmon reproduction are compared between the early 21 century and previous period. There is found that recent in­crease of the catches could not be reasoned by favorable changes of environments, decreasing of juveniles mortality either in the river or in the sea, extending of spawning grounds, growth of spawning stock or number of juveniles. The only possible reason for significant rise of the landings could be an increasing by-catch of transitory stocks.