Iturup Island Research Articles

The Colonization History of Iturup Island by the Red-Backed Vole <i>Craseomys rufocanus</i> according to the Analysis of the Cytochrome <i>b</i> (<i>cytb</i>) Fragment

The hypotheses on colonization history of red-backed vole of Iturup Island comparative analysis of distribution and number of haplotypes of mitochondrial cytochrome b gene (662 bp) in vole sampled at various sites along the Iturup Island perimeter and Hokkaido, Kunashir and Sakhalin Islands and adjacent regions of the mainlandhas been carried out. All studied samples from the Iturup Island (68) belonged to the only one haplotype most close to the haplotypes of voles from the Sakhalin Island. The only sample from the Kunashir Island, nearest to the Iturup Island possessed the same haplotype, three additional samples from this island have haplotypes related to haplotypes of voles from the Sakhalin Island and fall within the so called “Sakhalin” clade, while the majority of haplotypes of voles from the Kunashir Island appeared to be close to haplotypes of voles from the Hokkaido Island and make up with them one independent clade, genetically very different from clade of Sakhalin and Iturup samples. The obtained data on the genetic variability of voles from the Iturup Island provides convincing evidence in favour of the recent introduction of the red-backed vole C. rufocanus to the Iturup Island, most likely with sea transport from Sakhalin.

ANALYSES OF THE AVIFAUNA AND BIRD POPULATIONS OF THE ISLAND OF ITURUP, GREAT KURIL ISLANDS

Ecological patterns in the formation of the avifauna and bird populations of the Iturup Island were analyzed. Route counts were used along transects of unlimited width. As many as 116 bird species were registered, including 36% revealed to be ubiquitous, another 34% local and further 26% highly local. 71 species were shown to nest. The taxonomic structure of the avifauna, represented by species from 15 orders, corresponded to the zonal and landscape features of the island’s territories located at the eastern margins of northern Eurasia. Passeriformes (37%), Charadriiformes (22%), Anseriformes (9%), Procellariiformes (8%) prevailed. The zoogeographic peculiarity of the local avifauna was a combination of elements of the Far Eastern island, Pacific, Siberian and Chinese faunistic complexes, some Siberian-American and widespread species, as well as Japanese island endemics. The avifauna around the Iturup Island, formed by a system of general zonal-landscape and altitudinal-belt patterns, united ecological groups of marine and land species, including montane ones (n = 9). Local avifauna in coastal marine habitats included 41 species, vs 55 in forests, 37 in light forests, and 46 in tall grasses, the population density being 607, 785, 968, 518 individuals/km2, respectively. The similarity coefficients for the populations of forest habitats were 19–48%, vs 22% for light forests, 20–37% for tall grasses, while in the sea coast and adjacent water areas they amounted to 21–52%. The populations of terrestrial habitats were dominated by the Oriental Turtle-dove, the Pacific Swift, the Siberian Rubythroat, the Japanese Bush-warbler, the Marsh Tit, the Coal Tit, the Eurasian Nutcracker, the Oriental Greenfinch, the Eurasian Siskin, the Long-tailed Rosefinch, the Masked Bunting, and the Grey Bunting. The populations of the coast and adjacent sea area were dominated by the Japanese Cormorant, the Rufous-necked Stint, the Slaty-backed Gull, the Black-tailed Gull, and the Black-backed Wagtail. In open sea areas, the most common were the White-winged Scoter, the Black-footed and Laysan albatrosses, the Northern Fulmar, and the Short-tailed Shearwater.

HOLOCENE EXPLOSIVE ERUPTION ON THE VETROVOY ISTHMUS (ITURUP ISLAND) AS A SOURCE OF THE 2000 cal BP MARKER TEPHRA LAYER IN THE CENTRAL KURIL ISLAND ARC

Geochemical study of volcaniclastic material and radiocarbon dating of charred plant debris from Holcene deposits of the Guram site, which is located in vicinity of Vetrovoy Isthmus at Iturup Island, demonstrate that explosive eruption (VEI 4-5) occurred there by 2000 years ago. Geochemical and age similarity with the tephra of marker layer CKr that was distinguished at Iturup, Urup, Simushir, Rasshua, and Matua islands of the Kuril Island Arc led to the conclusion that this eruption is supposedly a source of this tephra. The data presented are proposed as a motivation for revision of volcanic hazard at Iturup Island.

Comparative characteristics for producers of pink salmon <i>Oncorhynchus gorbuscha</i>in the basin of Lake Sopochnoe

Pink salmon spawners in the channel connecting Lake Sopochnoe (Iturup Island) with the sea are investigated. The samples were collected in July-August, 2016. The males dominated significantly during entire spawning run. The fish became more and more ready for spawning with approaching to the end of the run. The average length and weight of females were 50.0 ± 0.3 cm and 1.53 ± 0.03 kg, the average length and weight of males — 50.2 ± 0.2 cm and 1.56 ± 0.02 kg; the fish caught in the channel were significantly larger than the pink salmon spawners caught in the adjacent Prostor Bay at the same time (on average 48.5 ± 0.1 cm, 1.32 ± 0.01 kg and 49.0 ± 0.2 cm, 1.40 ± 0.02 kg for females and males, respectively).

The Holocene Explosive Eruption on Vetrovoi Isthmus (Iturup Island) as a Source of the Marker Tephra Layer of 2000 cal. yr BP in the Central Kuril Island Arc

Geochemical study of volcaniclastic material and radiocarbon dating of charred plant debris from Holocene deposits of the Guram site, which is located in vicinity of Vetrovoi Isthmus on Iturup Island, demonstrate that an explosive eruption (VEI 4-5) occurred there about 2000 years ago. The geochemical and age similarity with the tephra of marker layer CKr that was distinguished on Iturup, Urup, Simushir, Rasshua, and Matua islands of the Kuril Island Arc led to the conclusion that this eruption is possibly a source of this tephra. The data presented are proposed as a motivation for revision of the volcanic hazard on Iturup Island.

SPECIES COMPOSITION OF PHYTOPLANKTON OF THE BLAGODATNOYE LAKE (ITURUP ISLAND, KURIL ISLANDS, RUSSIA)

Algological studies conducted in June–August 2021 on the lagoon Blagodatnoye Lake (Iturup Island) and showed a high diversity of species composition of cyanobacteria and algae (274 species and intraspecifi c taxa from eight divisions: Cyanobacteria, Miozoa, Bacillariophyta, Chlorophyta, Charophyta, Criptista, Ochrophyta, Euglenozoa). Diatoms make up a signifi cant share in the formation of algofl ora (73,2 % of the total number of species). Complexes of dominant species in lake plankton are represented by cyanobacteria and diatoms: Aulacoseira granulata and it’s variation A. granulata var. angustissima Aphanizomenon fl os-aquae (August). The maximum values of quantitative indicators of the main dominants reached: N = 1323,3 thousand cells/l, B = 685,5 mg/l for Asterionella formosa, and N = 3646 thousand cells/l, B = 4579,4 mg/l for Aulacoseira granulata. The ecological and geographical characteristics of the algal fl ora of Blagodatnoe Lake were carried out: benthic species (48,2 % of the total number of taxa), indiff erent to salinity change (68,6 %), alkaliphilic (42,3 %), cosmopolitan (70,1 %) species were predominance, and oligosaprobionts and betamesosaprobionts were 35,4 and 33,9 %, respectively.

FEEDING OF THE FISH OF BLAGODATNOE LAKE (ITURUP Island, KURIL ISLANDS) IN SUMMER

The feeding of mass fi sh species is described according to the data of ichthyological samples in June- August 2001 from Blagodatnoye Lake (Iturup Island, Kuril Islands):whitebaits of Oncorhynchus keta, Hypomesus nipponensis, Pungitius spp., Gasterosteus nipponicus, Salvelinus malma curilus, S. leucomaenis, Cottus amblystomopsis, Gymnogobius urotaenia and Tridentiger brevispinis. Whitebaits of Oncorhynchus keta, Pungitius spp. and Gasterosteus nipponicus formed the basis of catches in terms of abundance and biomass in the coastal zone of the lake. Hypomesus nipponensis is typical of shallow lake waters and has been constantly observed in the coastal area. Four ecological groups of fi sh are distinguished by the type of food. The fi rst group includes whitebaits of Oncorhynchus keta only, which are the most separated from other species in terms of the ecological spectrum of feeding. The basis of the diet of whitebaits of chum salmon (85 %) is non-aquatic insects consumed from the surface of the water. Salvelinus malma curilus and Hypomesus nipponensis exerted the greatest competitive pressure on juvenile salmon, 11 and 10 % of their diet also consisted of extra- aquatic insects, respectively. Hypomesus nipponensis is a plankto- benthophage and belongs to the second group. The basis of the ecological food spectrum of this species was formed by zooplankton (43 %) and zoobenthos (30 %). A signifi cant contribution was also characterized by fi sh eggs (17 %). The third group includes the Japanese three- spined sticklebacks, the main food of which is fi sh eggs (59 %) and zoobenthos (34 %). All other fi sh species are included in a single group of predominant benthophages. The contribution of zoobenthos in the ecological spectrum of nutrition of these fi sh varied from 57.4 % in Gymnogobius urotaenia to 100 % in Tridentiger brevispinis.

TRACE ELEMENT CONTENT IN THE PINK SALMON FROM THE RIVERS OF THE BARENTS AND OKHOTSK SEAS BASINS

The concentrations of Pb, Cd, Ni, Cu and Zn were determined in the invasive pink salmon that came to spawn into the Kola and Tuloma rivers of the Kola Peninsula, flowing into the Barents Sea, in July 2019. The content of trace elements in the organs and tissues of pink salmon introduced in the Euro-Arctic waters of Russia was compared to those of the pink salmon from its natural range, which returned to spawn in the rivers of the Sakhalin and Iturup Islands in 2016-2018. It has been established that concentrations of Zn, Cu and Ni noticeably predominate in all organs and tissues of introduced pink salmon, whereas Pb and Cd - in the Sea of Okhotsk pink salmon. Obviously, the differences in the microelement composition in fish are caused by environmental conditions. In the Barents Sea, they are formed under the influence of the Gulf Stream, as well as the anthropogenic impact of the Kola Peninsula, which is characterized by the extraction, processing and smelting of a number of metals, primarily Ni and Cu, as well as Zn. In the Sakhalin-Kuril basin, the specificity of the environment and the microelement composition of salmon are due to the influence of natural factors - volcanism and upwellings. Herds of pink salmon during feeding and migration in the Pacific Ocean cross a high-nutrient and at the same time geochemically impact natural zone formed by the Kuril Ridge and the Kuril-Kamchatka depression, which supplies chemical elements to surface waters. Here, the concentration of Pb is most markedly increased in fish. The development of the introduced pink salmon in the new area is facilitated by the recent increase in temperature in the waters of the North Atlantic, so the amount of fish production in it will increase. The mastering of pink salmon in new feeding places sets before scientists the task of monitoring the dynamics of its abundance, taking adequate measures for fishery regulation and fish quality control.

Morphology and Specific Features of Formation of Thermal Lake Utinaya Banya (Iturup Island, Southern Kuril Islands)

Abstract —This paper describes a set of studies performed at a thermal manifestation (Lake Utinaya Banya) on the Iturup Island (Kuril Islands). These studies include bathymetric survey of the lake basin, geometric leveling across the lake, pitting, sampling of thermal waters from the lake and springs, hydrochemical research, and isotopic analysis of oxygen and hydrogen in the lake water. It is suggested by the shape of the lake basin (close to lenticular with a significant concentric depression), the underwater gas-hydrothermal vents, the bank along the perimeter of the lake basin, and the presence of several layers of clastic deposits at the top of the rampart that the lake was formed by a hydrothermal eruption. The lake temperature has remained constant over the years and ranges on average from 25 to 15 °C, depending on the season. The water of Lake Utinaya Banya is represented by acidic, sulfate calcium, and low-mineralized waters.

Magnesian Basalts of the Medvezhia Caldera: Dominant Magmas and Their Sources, as Exemplified by Menshiy Brat Volcano, Iturup Island, Kuriles

Magnesian Basalts of the Medvezhia Caldera: Dominant Magmas and Their Sources, as Exemplified by Menshiy Brat Volcano, Iturup Island, Kuriles

LITTORAL ICHTHYOFAUNA OF MATUA ISLAND, KURIL ISLANDS

As part of the XXI Kamchatka-Kuril expedition of the Russian Geographical Society, with the assistance of the Russian Federation Ministry of Defense, a survey of the littoral ichthyofauna of Matua Island was carried out in 2017. Fishes were caught by hand under stones in tidal pools and with a net during low tide. Fishing was performed in three areas: Cape Klyuv, Cape Yurlova, and Dvoynaya Bay. The fish caught were fixed in 6% formalin. Laboratory processing was carried out: the total length TL was measured with an accuracy of 1 mm, weighed with an accuracy of 0.1 g. Representatives of the families Cottidae, Hexagrammidae, Liparidae, Pholidae, Stichaeidae, Zoarcidae were found in the littoral areas. The size characteristics of the family representatives discovered, and the areas and depth of their capture were presented. In the littoral zone, we found a number of species previously not recorded from this area in the literature. The species compositions of the littoral ichthyofauna of Paramushir Island, Matua Island, Iturup Island, Shikotan Island and Kunashir Island were compared. Only the Stippled gunnel, Rhodymenichthys dolichogaster and the Frog sculpin, Myoxocephalus stelleri were found shared by all those islands. The ichthyofauna of Matua Island shows the greatest similarity to that of Paramushir Island.

SNP-based discrimination of pink salmon stocks of the Sea of Okhotsk basin: resolution of the approach and possible ways to increase it

In this work, we studied the intraspecific polymorphism of pink salmon, Oncorhynchus gorbuscha (Walbaum, 1792), the least genetically explored species among Pacific salmon and one of the central fisheries objects in the Russian Far East. The most urgent task facing Russian fishery science is to determine the proportion of fish from the main reproduction areas in mixed stocks and, based on these data, predict the number of pink salmon returning to these regions for spawning. Due to the unique feature of the species, which evolved into two allochronous lineages, these lineages have been explored independently in parallel. We designed and used here two sets of outlier SNP markers, and this allowed us to reliably distinguish the most northern (Western Kamchatka and the Magadan coast) and the most southern (Iturup Island) regional stocks as well as intermediate stocks from Sakhalin Island and the Mainland coast in both even and odd lineages of pink salmon. In addition, in odd-year lineage, we discovered pronounced genetic differences between early-run and late-run spawners in Sakhalin Island and the proximity of this early spawning form to the mainland stocks. The created baseline covers the main areas of pink salmon reproduction in the Sea of Okhotsk basin and underlies the regional identification of pink salmon in mixed marine stocks.

Magnesian Basalts of the Medvezhia Caldera: Main Magmas and Their Sources on the Example of the Menshiy Brat Volcano (Iturup Island)

The paper represents new data on the formation conditions of basalts from post-caldera volcano Menshiy Brat (Medvezhia caldera, Iturup Island). Liquidus mineral assemblage is composed of olivine (Fo up to 90.1 mol. %) and chromium spinel (Cr# = 0.46–0.6), which crystallized at 1090–1170°С and oxygen fugacity NNO +0.6 (σ = 0.2) – NNO +0.2 (σ = 0.14). The study of melt inclusions in the liquidus olivine demonstrated that its parental melts have low-alumina, low-potassium compositions with up to 15.5 wt. % MgO and with an average water content of 5.5 wt. %. The data on volatile contents in the olivine-hosted melt inclusions suggest that the basic melts appeared due to partial melting of essentially peridotitic source with a small admixture of an olivine-free component at 1225°С under active influence of the slab-related fluids. These fluids were separated from the subducting slab at 670–705°С and depths of 95–105 km beneath the Iturup Island. The results of this study enhance our understanding of the evolution of basic magmas that serve as a heat and volatile supply during the formation of large calderas.

Factors Determining the Replenishment of Pink Salmon Oncorhynchus gorbuscha (Salmonidae) on Iturup Island

Based on the data on the abundance of 53 generations of pink salmon Oncorhynchus gorbuscha of Iturup Island (spawners on spawning grounds, downstream migrating juveniles and the return of mature fish), a model describing the dependence of the abundance of mature pink salmon offspring on the initial abundance of generations and the effect of external factors was constructed using nonlinear regression analysis. The model explains about 80% of the replenishment variability, and it depends more on the effect of external factors in the freshwater period of life. The variability of replenishment is most closely related to factors related to the hydrological regime of rivers. The dependence of replenishment on the abundance of juveniles migrating downstream from spawning grounds, described by the dome-shaped curve, indicates the limiting effect of density factors on the formation of the abundance of pink salmon during the marine period of life. At the same time, a statistically significant effect of the abundance of juveniles released from fish hatcheries on the dynamics of the replenishment was not found.

The phylogenetic position of Maritrema afanassjewi Belopol'skaya, 1952 (Digenea, Plagiorchiida: Microphallidae), a parasite of the Ussuri brown bear, Ursus arctos lasiotus Gray, 1867 (Carnivora, Ursidae)

Adult digeneans of Maritrema afanassjewi Belopol'skaya, 1952 parasitize birds and mammals along the North Pacific coasts and were previously studied in terms of morphology. However, morphological features not supported by molecular characterization are considered an insufficient tool for the identification of evolutionary lineages of microphallid digeneans. Here we provide the first data on the phylogenetic position of this species inferred from sequences of the 28S rRNA gene and the ITS2 locus of the nuclear DNA, as well as additional morphometric data. The trematodes were isolated from the intestine of the Ussuri brown bear ( Ursus arctos lasiotus Gray, 1867) on Iturup Island (the southern Kuril Islands). This is the second record of M. afanassjewi in the brown bear. The phylogeny based on the 28S rRNA gene was poorly resolved for this parasite species. The analyses based on the ITS2 locus dataset showed that M. afanassjewi was a low-supported sister to Maritrema subdolum Jägerskiöld, 1909.

Characteristics of spawners of chum salmon <i>Oncorhynchus keta</i> from commercial stock of Iturup Island

Chum salmon spawners returned for spawning in the rivers of Prostor and Kurilsky Bays on Iturup Island (Kuril Islands, Sakhalin Region) were examined in the period from September 19 to November 4, 2022. Both females and males had mostly the age 3+ (68.8 % in the Prostor Bay and 62.2 % in the Kurilsky Bay). The portion of males in the age 2+ was in 3.8 times higher than the portion of females, with the average value of 19.2 %; the summary portion of older age groups (4+ and 5+) was 15.4 %. Chum salmon spawners were distinguished by relatively small body weight, similar for the fish of the same age in both bays, on average 2.27 and 2.57 kg for females and males of age 3+, respectively, that was lower than the weight of chum salmon spawners in the previous 8 years.

On coho salmon <i>Oncorhynchus kisutch</i> from Iturup Island

Results of biological analysis are presented for 162 specimens of coho salmon caught at the coast and in the rivers of Iturup Island (southern Kuril Islands) during their spawning migration in August-October, 2021. Almost all females and males close to puberty in the current year spent one year in the sea and were aged 1.1+ (66.7 %) and 2.1+ (30.0 %). The fish that spent two years in the sea were single – 1 specimen aged 1.2+ and 3 specimens aged 2.2+ (2.5 %). Taking into account the age of puberty and the body weight (2.63 kg for females and 2.44 kg for males, on average) the spawners reproduction in short streams is assumed. The high value of the gonad-somatic index (up to 20–22 % for some females) is other evidence that all these fish cannot run to other spawning areas but at least a part of them should spawn in the water bodies of Iturup Island. Indeed, some coho salmon were captured directly in the rivers. Beside the spawning fish, two actively feeding coho females aged 0.0+ (0.55 kg) and 1.0+ (1.11 kg) were caught with fixed nets.

On state of commercial herd of chum salmon <i>Oncorhynchus keta</i> and forecasting its abundance at Iturup Island

Population dynamics and size-age structure are analyzed for the chum salmon herd formed in the Prostor and Kurilsky Bays of Iturup Island (Kuril Islands). Release of chum juveniles into the waters of the bays increased from 10.7.106 ind. in 1996 to 197.6.106 ind. in 2020. The catch of adults was closely related with the release of juveniles (r = 0.66) and increased from 800 t in 1996 to 18,968 t in 2019. Year-to-year dynamics of the chum salmon catch coincides in these two bays, i.e. strong year-classes provide good catch in both bays and low survival causes low catch everywhere. The spawners of age groups 2+ and 3+, mostly 3+ (62 %, on average) dominated in the catches in 2014–2022. This feature makes available the forecast of chum salmon landing in the Prostor and Kurilsky Bays because of strong dependence of annual catch of fish at the age 3+ on the catch at the age 2+ in preceding year (r = 0.89; rs = 0.98). Besides, a significant relationship is noted between the annual catches of chum and pink salmon belonged to the same year-class, i.e. between the catches of chum salmon at the age 3+ and the catches of pink salmon in preceding year (r = 0,71; rs = 0,75).

Predictions about the Pink Salmon Oncorhynchus gorbuscha (Salmonidae) Catches on Iturup Island

The pink salmon Oncorhynchus gorbuscha spawners which otolith marks created at fish early age at the Kurils and Reidov fish-rearing stations have been studied; fish breeding data and fishing statistics have been analyzed. At the end of the spawning run of pink salmon, only fish of the fish-farm origin have been caught near the fish-rearing stations. More than that, the pink salmon spawners return to the stations of their release (although with rare exceptions). The catches of the pink salmon on Iturup Island are on average 1.6 times greater in even years than in odd years. The increase of the fish stock in odd years significantly depends on the breeding of juveniles in fish farms. There is a positive statistically significant relationship between the filling of spawning grounds with pink salmon spawners and its catches in the Prostor and Kurilsky bays two years later.

Some data on the fishery, distribution and size composition of saffron cod Eleginus gracilis Tilesius, 1810 near the Southern Kuril Islands

Data on harvesting, seasonal dynamics, structure of coastal and marine fishery, size and age composition of saffron cod catches near the Southern Kuril Islands are given. Summer–autumn distribution and size composition of saffron cod aggregations is considered based on the data of bottom trawl surveys. Distribution of saffron cod is shown almost everywhere near Kunashir Island, the Lesser Kuril Ridge and Pacific coast of Iturup Island. Harvesting is provided throughout the year, but mainly at December fishing for bottom and demersal fish species in the South Kuril Strait and May–June fishing with small fixed nets near Kunashir. Although catches of saffron cod have increased in recent years, the species is still under exploited commercially.