Intraspecies Groups of the Chum Salmon Oncorhynchus keta (Salmonidae) of the Amur River and Their Distribution within the Basin

Abstract

The chum salmon in the Amur River basin is represented by two races, that is, summer-run and fall-run races. In the summer-run race, one population is known to use a specific type of spawning grounds. The fall-run race includes three populations with different types of spawning grounds. These four populations correspond to four eco-geographical groups separated reproductively by geographical boundaries of the geomorphological zones, as well as temporally and ecologically. In China, chum salmon has not been recorded from the spawning grounds of the Amur basin for already more than 50 years. In the Russian Federation, 100% of summer-run chum salmon spawn completely at parafluvial springs in late July and August; 77.1% of fall-run chum spawn at orthofluvial springs in September–November; 20.4% of fall-run chum spawn in the downstream part of the spawning range at parafluvial springs in September; and 2.5% of fall-run chum spawn in lakes near the Amur River mouth at orthofluvial springs in October and November.