Том 45, № 1 (2019)

The on-shore haul-out of phocid seals located in the mouth of Piltun Bay (northeastern Sakhalin Island) has been studied and the number of seals on it during the ice-free season was estimated. Currently, it is the largest mixed-species on-shore haul-out on the northeastern Sakhalin coast. In the summer and autumn, three species of ice-bound seals feed in the adjacent waters: the bearded seal, ringed seal, and spotted seal. In 1999 and 2014–2017, the total observation time amounted to 630 days, during which 3361 counts of seals were made. The seasonal dynamics of the number of seals on shore are characterized by three consecutive periods with peak values (June–July, August–September, and October), each coinciding in time with the runs of anadromous fish through the bay mouth. In 1999, the number of seals was statistically significantly different from those recorded in 2014–2017; in 2014, it differed from the value in the season of 2016. In 1999, the median of the total number was significantly lower than in any of the seasons from 2014 to 2017.

This paper presents a comparative analysis of the variability of genetic characteristics in samples from the largest stocks of the Atlantic cod Gadus morhua Linnaeus, 1758 in the Northeast Atlantic (NEA) and the Northwest Atlantic (NWA) waters. The results of a pairwise estimation of the genetic differentiation, performed using allozyme and microsatellite markers, detected a significant difference between the cod sample from the New England Shelf (NWA) and the cod of the Icelandic–Greenlandic and Norwegian–Barents Sea stocks. At the same time, cod samples from areas of East and West Greenland and samples from the Barents Sea, despite considerable geographic differences, demonstrated a high level of identity according to molecular genetic markers. The peculiarities of the formation of the cod population structure in the Quaternary period are considered in connection with the dynamics of global climatic and oceanological processes.

The relationships of the stone charr Salvelinus malma kuznetzovi, an endemic taxon to the Kamchatka River basin, were inferred from analysis of the nucleotide sequences of the mitochondrial DNA control region (CR) and cytochrome b (Cytb) and cytochrome oxidase-1 (COI) genes, as well as the nuclear lactate dehydrogenase gene (LDH-C1). Genealogical analysis of mtDNA haplotypes confirmed the phylogenetic closeness of S. m. kuznetzovi, S. albus, and S. m. malma and showed that the above taxa represent the Beringian phylogenetic group of charr. The level of mtDNA divergence between S. m. kuznetzovi, S. albus, and S. m. malma did not exceed the intraspecific variation in Northern Dolly Varden populations. The existence of a cryptic Pleistocene refugium in the Kamchatka River basin has been substantiated; nevertheless, extensive and complex studies of charr of the Beringian group are needed.

To estimate the genetic variability of the pink salmon Oncorhynchus gorbuscha (Walbaum, 1792) of even-year broodlines from the Bakhura River, Sakhalin Island, the polymorphism of nucleotide sequences of the ND2 and Cytb genes (mtDNA) with a total length of 1809 bp has been analyzed. In 211 pink salmon specimens from three samples of different years, a total of 44 haplotypes at 39 polymorphic sites have been identified. The neutrality tests indicate a high probability of purifying selection in the studied genes. The analysis of mismatch distribution, the neutrality tests, and the Bayesian skyline data support the expansion model for the even-year broodline pink salmon population. The study of the haplotype divergence history based on Bayesian chronogram shows that the divergence within the main phylogroups occurred in the intervals of 40 400–54 300 and 4800–25 000 years ago.

Population dynamics parameters of Rastrelliger kanagurta (Cuvier, 1816) were analyzed from January to December 2008 in coastal waters of Pakistan. FiSAT software was used to assess growth population dynamics parameters. The growth parameters K = 0.84 year^–1 and L∞ = 24.57 cm were estimated with the aid of von Bertalanffy growth function. The natural mortality rate (M), the fishing mortality rate (F), and the total mortality rate (Z) were calculated as 1.682, 2.208, and 3.890 year^–1, respectively. The annual instantaneous fishing mortality rate in our study was considerably greater than both the target (F_opt = 0.841 year⁻¹) and limit (F_limit = 1.121 year⁻¹) biological reference points, suggesting that this species is being over-exploited in the waters of Pakistan. An exploitation rate (E) was estimated to be 0.567 year^–1and longevity (t_max) was calculated as 3/K equal to 3.57 years. The fishery of R. kanagurta by the gillnet catches in our study are of ages 2 to 3 years which indicated a reasonable mesh size for the catch.