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Ecoregion Description

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Species Richness

# of Endemic Species


641: Sakhalin, Hokkaido, & Sikhote - Alin Coast

Major Habitat Type:

temperate coastal rivers


Nina Bogutskaya


China; Japan; Russia


The ecoregion includes all but the northwest coast of Sakhalin Island (excluding the Amurskiy Liman Strait basin and the southern coast of Sakhalinskiy Bay), Hokkaido Island, and the southern Kuril Islands (from north to south: Ostrova Chernyye Brat’ya, Urup, Iturup, Kunashir, Shikotan, Zelenyy, and Habomai islands).

The continental part of the ecoregion encompasses coastal rivers of the Sea of Japan from south of the Amurskiy Liman Strait (Zaliv Chikhacheva Bay) down to the Tumen-Ula [Tumannaya = Tuman-gang] (Lake Khasan inclusive). The western border of the ecoregion (with Lower Amur [616]) runs along the dividing ranges of the Sikhote-Alin’ Mountains (from north to south): Sredinnyy Khrebet, Golyye Gory, and Bolshoy Yang. The southwestern border follows the Khrebet Przhevalskogo Range and the northwestern slopes of the Nangang Mountains.

Drainages flowing into:

Sea of Okhotsk (northern Pacific Ocean), Sea of Japan (eastern Pacific Ocean)

Main rivers or other water bodies:

Sakhalin (from north to south): 1) western coast: Tyk River, Krasnogorka River, Ayskoye Lake, Aynskaya River; 2) eastern coast: Piltun River, Tym’ River, Nabil’ River, Navskoye Lake, Poronay River, Busse Lagoon, Lyutoga River.

Maritime coast (from north to south): Muty River, Tumnin River, Samarga River, Edinka River, Kaban’ya River, Kema (Velikaya Kema) River, Serebryanka River, Avvakumovka River, Kievka River, Partizanskaya River, Razdol’naya [Suyfun = Suifen He] River, Tumannaya [Tumen-Ula = Tuman-gang] River.

Kurils (from north to south):  Lake Krasivoye (Iturup Island); Lake Peschanoye, Lake Lagunnoye (Kunashir Island).


The Sikhote-Alin Mountains stretch along the continental portion of the ecoregion, with elevations reaching over 2000 m.

The Kuril Islands extend from Cape Lopatka (50° 56’ N and 156° 30’ E) of the Kamchatka Peninsula down to Hokkaido Island (40° 25’ N and 145° 24’ E), dividing the Sea of Okhotsk from the Pacific Ocean. The total length of the island chain is around 1200 km. There is an additional chain of small islands (the Lesser Kuril Ridge) 100 km long along the southern coast of Kunashir Island. There are over 30 islands, but only 10 of them are larger than 200 km2. There are also a number of rocks.

Sakhalin lies off the East Asian coast between 54° 24’ N (Cape Elizabeth) and 45° 54’ N (Cape Krilion) for a distance of 948 km. The maximum width of Sakhalin reaches 157 km, and the minimum width in the narrowest part of the Schmidt Peninsula is 6 km. The average width of the island is approximately 100 km, and its area is 76 400 km2. The northwestern part of the island nearly adjoins the continent, and is only separated from it by the shallow Nevelsky Strait, with depths of 7-12 m. The southern part of Sakhalin is separated from Hokkaido by only 40 km at the La Pérouse Strait, its average depth being approximately 60-70 m.

Much of the relief of Sakhalin is relatively diverse and complex. In the southern and central part of the island mountains of average altitude (500-800 m) are predominant, and only a few peaks exceed 1000 m. The Eastern Sakhalin Mountains, stretching from the Terpeniya Peninsula in the south up to the Nabil River in the north, are a major mountain chain in Sakhalin.

The Kuril Islands are located within a tectonic and volcanic zone that is characterized by a combination of young active volcanoes and adjacent deep oceanic hollows. The surface structure of the Kuril Islands is largely determined by ancient and recent volcanic activity connected with tectonic breaks. About 160 volcanoes can be counted today, 40 of which are currently active. Often lakes are located in craters of volcanoes.

Bussol Strait (over 2000 m deep), lying between Urup and Simushir islands in the central Kurils, is the most significant biogeographic boundary within the Archipelagho, and divides the Archipelago into two parts, the northern one, which belongs to the Kamchatka & Northern Kurils ecoregion [613], and the southern one, which belong to this ecoregion.

The largest southern Kuril Islands (from north to south) are Urup, Iturup, Kunashir, and Shikotan. The islands are separated from eachother by shallow straights. Most islands contain one to several lakes, which are connected by a stream to the sea or are isolated.

Tectonic structures formed the relief of the islands. Thus, the Eastern Sakhalin composite anticline includes the Easterm Sakhalin Mountains, which stretch from the Schmidt Peninsula up to the Tonino-Aniva Peninsula on Sakhalin Island. The Western Sakhalin composite anicline conforms to the Western Sakhalin Mountains. The Central Sakhalin synclinorium forms a system of intermontane depressions that stretch in a sublongitudinal direction. These tectonic depressions are Baikalskaya, Tym’-Poronaiskaya, and Susunaiskaya. They continue further south on Hokkaido Island, which together with Sakhalin represents a single elevation of the Cenozoic folded system.


As a consequence of the varied impacts of land and sea that change from season to season, the atmospheric circulation in the ecoregion is of pronounced monsoon character. The mean annual air temperature varies from -2.0 – 2.7 °C in the north to 4.0 –  4.5 °C in the south. Precipitation is distributed unevenly throughout the ecoregion as well as by season. The major portion of precipitation falls during summer and autumn, whereas the least amount of precipitation falls in January and February. Excess humidity in lowlands and river valleys leads to waterlogging in those areas.

The climate in the region of the Tumannaya River (Tumen River) is cool temperate with considerable seasonal fluctuations in precipitation and temperature. Annual precipitation is 600-900 mm, the majority falling in June – August. The water level in the river during the spring tide rises by 0.5 - 2 m, and in the summer and autumn during rain floods, by 2.5 - 6 m.

The climate of the Kuril Islands is predominantly oceanic temperate, with relatively abundant precipitation and a low annual mean temperature.

Freshwater habitats:

The rivers of the ecoregion are characterized by a relatively low spring tide, heavy summer floods, and particularly low winter mean water. The regime of Sakhalin\'s rivers is complex, reflecting three stages of flood. Spring flood is caused by snowmelt within the plain parts of drainages; in early summer, the flood is formed by mountain snowmelt; and, eventually, middle summer (July – August) floods are caused by monsoon rains.

Many of the ecoregion’s rivers are of mountain character in the upper reaches and of plain character in the lower reaches. The rivers normally freeze in November – December and break up in April or May.

Water bodies of Sakhalin are diverse, comprising more than 16 000 lakes of various types, including water erosion (bayous), water-accumulative (delta and lagoon), dammed, holed (thermokarst), anthropogenic (reservoirs), and volcanic, with a total surface area of 1004 km2. The overwhelming majority of the lakes have surface areas less than 0.4 km2 and are associated with low and plain regions. A number of large lakes are of marine origin. They were formed by surf waves that inwashed sand beaches (dunes), separating the bays from the sea. The largest of these lakes are Nevskoye, Tonnai, Ainskoye, Vavaiskoye, and Sladkoye. In the North-Sakhalin Lowland, on the coast are large lagoons, small bays, Lunskii, Nabilskii, Nyiskii, Chaivo, and Piltun, which are separated from the sea by sand-pebble spits, sometimes attaining considerable width. There are thermokarst lakes in the northern part of the island, and bayous in its middle part, particularly in floodplains of the Tym (280 km) and Poronai (250 km) rivers.

South of the Amur River estuary up to the frontier with Korea many relatively small rivers, flowing from the eastern slopes of the Sikhote-Alin, fall into the Sea of Japan. They all have a mountain character of flow, large slopes, and high flow velocities. The largerst of these rivers is the Tumnin River, which is 270 km in length and 22 400 km2 in drainage area. Catchment areas of other rivers of this group do not exceed 6000-7000 km2.

In the region of Vladivostok, the Suchan, Maikhe, and Suifun [Razdol’naya] rivers fall into the Peter the Great Bay. The largest of these is the Suifun River, with a length of 288 km and drainage area of 18 450 km2. The Tumannaya River flows along the frontiers of Russia, China, and Korea. It begins on the eastern slopes of the extinct Pektusan Volcano on the Chanbaishan Plateau. The length of the river is 516 km, and catchment area is 33 168 km2. Due to large fluctuations in atmospheric precipitation, the major part of which falls from July through August, and shallowness of rivers in winter, the flow throughout the year changes ten-fold. A large part of the Tumannaya River drainage is situated in highlands, which accounts for its high flow velocity. The main tributaries of the Tumannaya River are the Gaiya, Buerkhaton, Khailan, and Khunchun (left tributaries) rivers. A large part of the catchment area of the Tumannaya River lies at an altitude of 400-1000 m in the uplands, covered by forest and shrubs with narrow valleys. Approximately 40-50 km from the estuary the lower Tumannaya River has a plain character. This area includes extensive floodplains and marshlands abounding in lakes and lagoons. The river width varies from 200 m around 20 km upstream from the estuary, up to 1500 m within the esuary.

Water bodies of the Kurils represent a wide variety of relatively small streams and lakes that are connected to the sea. Some of them are influenced by volcanic activity.

Terrestrial Habitats:

The terrestrial ecoregions include Okhotsk-Manchurian taiga (north) and Ussuri broadleaf and mixed forests (south) along the Maritime coast; Sakalin Island taiga (north) and South Sakhalin-Kurile mixed forests (southwest) on Sakhalin Island; Hokkaido montane conifer forests and Hokkaido deciduous forests on Hokkaido Island; and South Sakhalin-Kurile mixed forests and Kamchatcka-Kurile meadows and sparse forests on the south Kuril Islands.

Fish Fauna:

The ecoregion’s fish fauna includes nearly 90 species from over 20 families.  The most predominant are migratory Cypriniformes, euryhaline Gobiidae, Cottidae, and Salmonidae. The fauna of the ecoregion has a peculiar characteristic of being unique, but intermediate between the main distinct zoogeographic units around the ecoregion – Kamchatka-Siberia, Amur River drainage, Sakhalin-Hokkaido, river basins of the continental coast south from Amur, Korean Peninsula. Thus, the ecoregion includes a relatively large number of species that are originally marine (mostly migratory) and euryhaline forms. The number of residential, originally freshwater, forms is much fewer than in large river drainage systems of Amur or Siberia. The diversity of freshwater, amphidromous, or euryhaline gobiids is characteristic of the ecoregion.

The ecoregion can be subdivided into more or less distinct subregions, Northern and Southern Maritime territories, three subregions on Sakhalin Island, Hokkaido, Tumannaya River, and southern Kuril Islands. Each supports its own endemic forms.

Description of endemic fishes:

There are eight endemic species in the ecoregion, including two Gymnogobius (G. petschiliensis and G. taranetzi) and two Cottus (C. czerskii and C. volki) species. Others include forktongue goby (Chaenogobius annularis), Gobio macrocephalus, Pungitius polyakovi, and seaweed pipefish (Syngnathus acusimilis). A large portion of the endemic forms are from the Cottidae and Gobiidae families, which are secondary freshwater or euryhaline. The systematics of many of them need further studies.

Other noteworthy fishes:

Acipenser medyrostris mikadoiis is an extremely rare and threatened fish. It is still known to enter a few rivers along the Sea of Japan coast for spawning.

Charrs of the Kuril Islands represent an interesting complex of brook, riverine, lacustrine, and migratory forms.

An undescribed species, Kunashir smelt (Hypomesus chishimaensis) (Kunashir Island) may be a distinct species from the southernmost islands of the Kuril Islands. It may represent a local lacustrine resident form of Japanese smelt (Hypomesus nipponensis).

Other noteworthy aquatic biotic elements:

The fauna of freshwater molluscs in the Kuril Islands is relatively numerous. There are six known endemic species that account for 7% of the species known to inhabit the Kuril Archipelago. The presence of this comparatively diverse fauna of freshwater molluscs when primary freshwater fishes are completely absent is surprising given the palaeogeography of the region.

Ecological phenomena:

The distribution of species in rivers of the ecoregion is mosaic, correlated with the size of the river drainage. In shallow rivers the number of fish species is lower than in large rivers. Primary freshwater fishes are absent in the Kuril Islands.

Evolutionary phenomena:

The dynamic history of geological transformations affected the faunal composition of the ecoregion. Primarily, the alternating regressions and transgressions of the sea had a catastrophic impact on freshwater hydrographic systems, leading to their complete destruction. Spatial partitioning, isolation, and rapid colonization provided prerequisites for accelerating the evolutionary processes in the ecoregion.

A comparison of the Kuril’s fish fauna with those of the Maritime Territory, lakes of Sakhalin, and Japanese islands demonstrates a remarkable depletion due, first of all, to the absence of pure freshwater fishes. It may be caused by the inundation of valleys within the islands during the latest sea transgressions. This is an interesting area for studying the mechanisms of speciation in conditions of relatively recent spatial isolation in different groups of ancestors.

Justification for delineation:

As early as 1889 A.M. Nikolskiy concluded that in the Pleistocene Sakhalin and Hokkaido islands on the one hand, and the Japanese islands (Honshu and islands south of it) and Korea on the otherhand, were two peninsulas of the Asian continent separated by the sea at the present Tsugaru Strait. An analogous correlation of land and sea could have existed in the Late Miocene, Late Pliocene through the Early Eopleistocene, and in the cold epochs of the second half of the Pleistocene (Pletnev 2004). During the “cold” Pleistocene (0.7-0.01 mya) repeated climatic changes (thermo- and cryochrones) and wide-range fluctuations of the sea level, from -130 m to 10-15 m, were noted.

During the cryochrones (60 000 - 40 000 and 22 000 - 11 000 years ago) glacioeustatic a sea level decline of 100—130 m occurred, which led to the closing of the shallow Nevelsky and La Pérouse straits and the origination of isthmuses in their place. The last post-glacial transgression, which began 15 000 - 17 000 years ago, developed rapidly, with an initial rise in sea level up to 9 m per 1000 years. As a result, in less than 10 000 years the sea level reached present levels or even slightly higher levels, after which the rate of the transgression slowed down abruptly. The La Pérouse Strait and Nevelsky Strait opened, 12 000 - 11 000 years ago and ca 7000 years ago respectively, and Sakhalin became an island again.

The wide-ranging changes of sea level in the “cold” Pleistocene repeatedly led to the joining of Sakhalin with the continent and Hokkaido Island. The most favorable conditions for penetration of thermophilous elements into Sakhalin occurred in the Eopleistocene. For the dispersal of cryophilous elements of the biota, cold epochs of the Late Pleistocene were preferable, when sea level declined to 110 - 130 m and mean annual temperature was 7~9 °C lower than present.

There are objective historic prerequisites for joining all of the subregions in question into one ecoregion. It includes a relatively large number of species with a predominance of originally marine (mostly migratory) and euryhaline forms. The number of residential, originally freshwater, forms are much fewer than in large river drainage systems of Amur or Siberia. The diversity of freshwater, amphidromous, or euryhaline gobiids is characteristic of the ecoregion.

Level of taxonomic exploration:



Aleksandrov, S. M. (1973). "Sakhalin Island" Moscow: Nauka.

Nikiforov, S. N., Grishin, A. F., et al. (1997). "Fish fauna composition and distribution of fishes in rivers Tym' and Poronay" Voprosy Ikhtiologii [J. Ichthyol.] 37(3) 329-337.

Nikiforov, S. N., Makeyev, S. S., et al. (1994). "Freshwater fish fauna of South Sakhalin and its origin" Voprosy Ikhtiologii [J. Ichthyol.] 34(1) 24-41.

Pietsch, T. W., Amaoka, K., et al. (2001). "Freshwater fishes of the Kuril Islands and adjacent regions" Species Diversity 6 133-164.

Pietsch, T. W., Bogatov, V. V., et al. (2003). "Biodiversity and biogeography of the islands of the Kuril Archipelago" Journal of Biogeography 30(9) 1297-1310.

Shed’ko, S. V. (2002)"Review of freshwater fauna" In Flora and fauna of Kuril Island (materials of International Kuril Island Project). (pp. 118-134)

Shed’ko, S. V. (2001). "List of cyclostomata and fishes of fresh waters of Primorsky Territory coast" Paper presented at the V.Y. Levanidov’s Annual Mem. Meetings

World Wildlife, Fund (2001). "Terrestrial Ecoregions of the World" 2005 (2005;

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