Sakhalin taimen (Parahucho perryi) range from the Russian Far East mainland along the Sea of Japan coast, and Sakhalin, Kuril, and Hokkaido Islands and are considered to primarily be an anadromous species. We used otolith strontium-tocalcium ratios (Sr/Ca) to determine the chronology of migration between freshwater and saltwater and identify migratory contingents of taimen collected from the Koppi River, Russia. In addition, we examined taimen from the Sarufutsu River, Japan and Tumnin River, Russia that were captured in marine waters. Transects of otolith Sr/Ca for the Sarufutsu River fish were consistent with patterns observed in anadromous salmonids. Two fish from the Tumnin River appeared to be recent migrants to saltwater and one fish was characterized by an otolith Sr/Ca transect consistent with marine migration. Using these transects as benchmarks, all Koppi River taimen were classified as freshwater residents. These findings suggest more work is needed to assess life history variability among locations and the role of freshwater productivity in controlling migratory behavior in taimen.

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Hierarchical population structure can result from range-wide geographic subdivision under conditions of environmental heterogeneity and weak gene flow. While a lower level of structure can be formed by local populations within eco-geographic regions, an upper level can be characterized by variation between populations from different regions, and thus, be represented by evolutionarily significant units (ESUs) defined by environmental, ecological and genetic variation. Selection of ESUs may depend on the sequence of using these three sources of variation. We propose to determine ESUs by first using non-genetic, ecological and geographical gradients for defining preliminary population groups (eco-geographic units, EGUs) and then testing whether the boundaries of these units are genetically coherent and thus represent ESUs or warrant their further modification. We evaluate this approach using Sakhalin taimen, an East Asian endangered endemic fish. Forty-one samples (473 fish) were drawn from thirty populations across the species range and genotyped at microsatellite DNA markers. We assign the populations into ESUs based on geographic and life history criteria and subsequent application of genetic diversity analyses. The ESUs appeared to be greatly diverged genetically. Within ESUs, local populations are genetically differentiated, have low effective sizes, show signatures of demographic decline and extremely restricted gene flow. Conservation plans aimed to restore or maintain a specific threatened population should take into account such hierarchical structure, and in particular be based on the genetic resources drawn from each population or using ecologically and genetically similar populations from the same ESU as donors for restoration of the population.

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Chum salmon in the Amur River basin are represented by two races: summer and fall ones. For the summer race, one population with specific type of spawning grounds is known, but the fall race includes three populations with different types of spawning grounds. In total, four eco-geographical groupings of the species are separated in their reproduction by geographical boundaries of geomorphological zones, as well as temporally and ecologically. Chum salmon do not spawn in the Chinese part of the Amur basin in more than 50 years. In the Russian part, the summer chum salmon spawn completely in the hyporheic waters in late July — August, the major grouping of fall chum (77.1 %) spawns in the spring waters in September-November, other two groupings spawn in the hyporheic waters of the lower Amur in September (20.4 %) and in the spring waters of the lakes near the Amur mouth in October-November (2.5 %).