The length–age distributions and genetic variation of ten microsatellite loci were examined in samples of herring from the Chupa Inlet of the Kandalaksha Gulf of the White Sea. The samples were collected on the same spawning grounds over a period of 13 years and during the same spawning season. The obtained data demonstrate stability of the length structure and genetic characteristics (allele and genotype frequencies, allelic richness, and heterozygosity). The degree of temporal genetic differentiation was not statistically significant, θ = 0.0038 (CI,–0.0006 to 0.006). Spatial differentiation of the White Sea herring far outweighs the level of temporal variability, which makes it possible to suggest the important role of reproductive isolation in the formation of the population genetic structure of herring.

The Solovetsky Islands are located in the central part of the White Sea (Arctic Ocean). The species composition and distribution patterns of freshwater ichthyofauna were studied in various watersheds of the two biggest islands of the Solovetsky Archipelago, Bolshoi Solovetsky and Anser, affected differently by economic activities. The research was performed in 1989–2012; in total, 40 lakes were studied. Two main groups of species were defined in regard to the original and historical data, aboriginal and introduced. Aboriginal species include rainbow smelt (Osmerus mordax), perch (Perca fluviatilis), pike (Esox lucius), roach (Rutilus rutilus), burbot (Lota lota), crucian carp (Carassius carassius), sticklebacks (Gasterosteus aculeatus, Pungitius pungitius), and ruff (Gymnocephalus cernuus). Sterlet (Acipenser ruthenus), brown trout (Salmo trutta), vendace (Coregonus albula), tench (Tinca tinca), and goldfish (Carassius auratus) are the introduced species. The origin of whitefish (Coregonus lavaretus) and ide (Leuciscus idus) remains unknown. The current distribution of all studied species is patchy and varies significantly between the lakes, and the origin of particular species should be found individually for each lake.

The genetic diversity among spawning groups of herring from different parts of the White Sea was assessed using ten microsatellite loci. All loci were polymorphic with the expected heterozygosity estimates varying in the range of 12.7–94.1% (mean was 59.5%). The degree of genetic differentiation displayed by White Sea herring was statistically significant (θ = 2.03%). The level of pairwise genetic differentiation F ST was 0–0.085, and it was statistically significant in most of the comparison pairs between the herring samples. A hierarchical analysis of molecular variance (AMOVA) revealed the statistically significant differentiation of White Sea herring. 96.59% genetic variation was found within the samples and 3.41% variation was found among the populations. The main component of interpopulation diversity (1.85%) falls at the differences between two ecological forms of herring, spring- and summer-spawning. Within the spring-spawning form, the presence of local stocks in Kandalaksha Bay, Onega Bay, and Dvina Bay was demonstrated.

The genetic diversity among spawning groups of herring from different parts of the White Sea was assessed using ten microsatellite loci. All loci were polymorphic with the expected heterozygosity estimates varying in the range of 12.7-94.1% (mean was 59.5%). The degree of genetic differentiation displayed by White Sea herring was statistically significant (theta = 2.03%). The level of pairwise genetic differentiation F(ST) was 0-0.085, and it was statistically significant in most of the comparison pairs between the herring samples. A hierarchical analysis of molecular variance (AMOVA) revealed the statistically significant differentiation of White Sea herring. 96.59% genetic variation was found within the samples and 3.41% variation was found among the populations. The main component of interpopulation diversity (1.85%) falls at the differences between two ecological forms of herring, spring- and summer-spawning. Within the spring-spawning form, the presence of local stocks in Kandalaksha Gulf, Onega Bay, and Dvina Bay was demonstrated.

Variability of cod spawning and feeding schools from Kandalaksha Bay of the White Sea, was examined at six allozyme and eight microsatellite loci. The degree of genetic differentiation at allozyme loci constituted θ = 0.36% [95% bootstrap interval 0.0458; 0.6743]. The differentiation estimates obtained using microsatellite markers were higher, θ = 1.33% [0.057; 3.11]. It was demonstrated that the level of genetic diversity in the White Sea cod was lower than that established for the Atlantic cod from Barents Sea using the same set of allozyme and microsatellite markers. The genetic data obtained support the opinion that the White Sea cod is a reproductively independent group formed as a result of the Holocene dispersal of Atlantic cod.

Variation of microsatellite loci Cpa110, Cpa113, Cpa4, and Cpa7 was for the first time examined in Pacific-type herring Clupea pallasii from the White Sea (Cl. pallasii marisalbi), the Kara Sea (Cl. pallasii suworowi), the Sea of Okhotsk, and Lake Nerpich’e, Kamchatka Bay, northwestern Pacific (Cl. pallasii pallasii). All loci exhibitedhigh genetic diversity. The estimates of expected heterozygosity varied from 41.5 to 95.6% (mean, 82%). The level of pairwise genetic differentiation F st at all microsatellite loci varied from 0.005 to 0.076 (0.019, on average) and t was statistically significant (p < 0.05) in most of the pairs of herring samples. Estimates of genetic differentiation among the herring of one subspecies were lower than between the groups belonging to different subspecies.

An analysis of genetic variation is made according to four allozyme loci of reproductive (spawning) groups of oligovertebrate herring Clupea pallasii collected in various bays of the White Sea and the south-eastern part of the Barents Sea in 1995–2002. The temporal stability of genetic characteristics during several years is shown. The analysis of genetic variation revealed a significant difference between herring from the south-eastern part of the Barents Sea and spring-spawning and summer-spawning herring from inner bays of the White Sea. The analysis of geographic variation of genetic characteristics of spawning aggregations revealed the change in frequencies of alleles of loci LDH-2* and MDH-4* from the north-east to the south-west along the coast.

The method of determination of hemoglobin affinity for oxygen based on polarographic analysis and the method of half-saturation values P50 calculation are described. A special design of a polarographic cell is proposed for measurements in a wide temperature range. The results of temperature and pH dependences of the hemoglobin affinity for oxygen and erythrocytes of the White-Sea cod are presented.