Southeastern Hokkaido Research Articles

北海道厚真町におけるマダラチュウヒの観察例

A single male Pied Harrier Circus melanoleucos was observed on 18 August 1996 in grassland at Atsuma, southeastern Hokkaido. This is only the fourth record of this species from Hokkaido.

Focal Mechanisms of Intermediate-depth Earthquakes Beneath Southeastern Hokkaido, Japan Implications of the Double Seismic Zone

In this study, the focal mechanism solutions and spatial distributions of 100 intermediate-depth earthquakes are examined and discussed. These earthquakes occurred from 1985 to 1993 mostly in the upper and lower planes of the double seismic zone beneath the southeastern part of Hokkaido. The focal-mechanism solutions along with the spatial distribution of their epicenters as a function of depth and the minimum- and maximum-compressive stress directions confirm the following essential features; A double-planed deep seismic zone between the depths from 60 to 120 km has been clearly revealed in this region and the number of earthquakes located in the upper plane are less than those for the lower one. Low-angle thrust fault mechanism is dominant to a depth of about 55–60 km in the zone. At depths deeper than about 60 km focal mechanism solutions are mostly characterized by down-dip extension type or down-dip compression type in both lower and upper planes of the zone. Most of the earthquakes deeper than 60 km have dip-slip components and some of the solutions have significant strike-slip components, as well. Although the down-dip extensional-type events are dominant, seven events that are located on the lower plane are constrained as down-dip compression mechanism. The T axes of earthquake focal mechanisms on the lower plane show extension at about N40°E and N35°W, and the dip-angle between 25° and 70°, almost coincide with the dip of the subducting Pacific Plate in this region. We also investigate the statistical features of the stress directions of the earthquakes occurring both on the lower and upper plane after converting all the events onto the plane having the same strike and dip angle as the subducting lithosphere in the region. Seventy-two percent of the minimum compressive stress directions are oriented mainly in the NS or NNE- SSW directions (within 45° of the dip direction) at the plate surface of the lower plane and are almost parallel to the dip of the local slab in this region. The number of earthquakes located in the upper plane is less than that for the lower one. Those which occurred on the upper plane show various types of mechanism solutions. Weak systematic orientation is found in the direction distribution of stress in the upper plane.

Demersal fish fauna in the Doto nearshore waters, northern Japan: Species composition and seasonal variation

The species composition of demersal fish was studied in nearshore waters (33-116 m depth) of south-eastern Hokkaido, the coldest area around the Japan Archipelago due to the influence of the cold Oyashio Current, using bottom gillnet samples collected during October 1996, August 1997, May 1998 and September 1999. The water temperature just above the sea bottom in the study area was lowest (<2°C) during May and then rose through autumn (>14°C). Cottids were the most abundant family in terms of both overall biomass and number, but their gravimetric dominance decreased from May (84%) through October (14%), whereas pleuronectids and stichaeids increased. Of the 57 fish species sampled, plain sculpin Myoxocephalus jaok was the dominant species in terms of overall biomass, accounting for 29.0% of the total biomass, followed by horned sculpin Enophrys diceraus (19.5%), Kamchatka flounder Atheresthes evermanni (6.5%) and blackline prickleback Acantholumpenus mackayi (4.9%). Plain sculpin dominated during May and September, but its predominance was low during October (9.6%), when witch flounder Glyptocephalus stelleri (22.7%) and blackline prickleback (10.8%) became important. This seasonal change appears to reflect the annual life cycle events of the fish, such as spawning.

Habitat selection by larvae of a fluvial lamprey, Lethenteron reissneri, in a small stream and an experimental aquarium

Habitat selection by fluvial lamprey larvae, Lethenteron reissneri (Petromyzontidae), was studied in a natural stream and an experimental aquarium to clarify microhabitat requirements for future conservation of natural populations. A gross collection survey of lamprey larvae in the Monbetsu River, southeastern Hokkaido, Japan, revealed a remarkable bias toward distribution in sandy-mud beds. An analysis using Jacobs' electivity index showed that the larvae selectively utilized spaces having regard to shallow water, weak current, deep sandy-mud, and fine substrate particles. A comparison of microhabitat use between small- (≤5 cm) and large-sized larvae (>5 cm) indicated that the latter utilized the space with greater ranges in both water depth and substrate particle size than the former. Both the field survey and laboratory experiments on larval selectivity of physical habitat variables clearly demonstrated that substrate particle size was the most important variable for small-sized larvae whereas both water depth and substrate depth were more important for large larvae. These findings should be applicable in directing attempts at fluvial habitat restoration for conservation of this endangered lamprey species.

Distribution and abundance of the wren Troglodytes troglodytes in central and south-eastern Hokkaido

Distribution and abundance of the wren Troglodytes troglodytes in central and south-eastern Hokkaido

Variations in Fledging Body Weight and Wing Length of Russet Sparrow Passer rutilans in Two Different Habitats

Variations in fledging body weight and wing length of the Russet Sparrow Passer rutilans were studied in two different types of habitats, shelter belt and isolated forests, in south-eastern Hokkaido, Japan, during the breeding seasons of 1995 and 1996. Although neither body weight nor wing length at hatching were significantly different between the shelter belt and the isolated forests, body weight at fledging was heavier in the isolated forests than in the shelter belt. This differences in fledging body weight might be explained by the presence of a greater food supply in the isolated forests than in the shelter belt.

Distribution of Jay Garrulus glandarius brandtii in central and south-eastern Hokkaido

Distribution of Jay Garrulus glandarius brandtii in central and south-eastern Hokkaido

Distribution of Bullfinch Pyrrhula pyrrhula in south-eastern Hokkaido

Distribution of Bullfinch Pyrrhula pyrrhula in south-eastern Hokkaido

Food and feeding habits of Kuril and Largha seals in southeastern Hokkaido

Les investigations ont porte sur les contenus stomacaux de phoques, Phoca vitulina stejnegeri et Phoca largha, captures dans les filets de peche au saumon installes au large de la presqu'ile Nemuro, Hokkaido, de septembre a decembre. On a trouve que six especes de proies etaient communes a ces deux especes de phoques. Toutefois, les Phoca vitulina stejnegeri se nourrissent principalement de poissons vivant sur les fonds cotiers rocheux tels que Cottidae, Stichaenidae, Sebastes, et des cephalopodes comme Paroctopus hongkongensis; tandis que les Phoca largha mangent des poissons de types plus varies: pelagiques comme Cololabis saira, Sardinopus melanosticus, ou benthiques tels que Ammodytes personatus, Hypomesus pretiosus et Osmerus eperlaus mordax

Interactions between Kuril seals and salmon trap net fishery in the coastal waters of southeastern Hokkaido: K. Wada, S.-I. Hayama, T. Nakaoka & H. Uno, Marine Mammal Science, 7(1), 1991, pp 75–84

A dynamic simulation model describing long-term forest development under different grazing pressures is presented as an illustration of system analysis in forest grazing research. In this paper, a brief description of the model is presented as are some simulation results. The FORest GRAzing model (FORGRA) simulates monthly changes in the characteristics of herbaceous understory and individual trees in plots, based on underlying physiological processes. Special attention is paid to the simulation of diet composition in relation to ungulate species, food quality and food availability, and accounting for seasonal variation in these factors. The model is parameterized for 12 tree and shrub species, six species of the ground flora and four ungulate species: roe deer (Capreolus capreolus), red deer (Cervus elaphus), Highland cattle (Bos taurus) and Konik ponies (Equus caballus). The results presented in this paper concern the development of a pine forest (Pinus sylvestris L.) in the Netherlands under various grazing pressures over a period of 100 years. They show that even low densities of ungulates can have significant impacts on the regeneration and thereby on forest development. It is argued that this approach is generally applicable in forest grazing research, providing a means for quantitative interpretation of the interaction between herbivory and forest development.

Crustal structure across the Kurile Trench off south-eastern Hokkaido by airgun-OBS profiling

Summary. Seismic refraction profiles were shot across the Kurile Trench, south-east of Hokkaido, Japan. The experiment in a typical island arc-trench system, where the Pacific Plate subducts beneath Hokkaido, was designed to investigate the transition of crustal structure from oceanic basin to continental slope across the trench. High resolution data were obtained from a 9 litre airgun and multi-OBS system. They were processed through a series of operations: digitization, filtering, slant stacking, t-sum inversion, two-dimensional ray tracing, and comparison with synthetic seismograms. A typical oceanic structure composed of an unconsolidated sedimentary layer (P wavespeed of 1.8–2.2 kms−1, thickness of 0.5–1 km), layer 2 (3.1–5.8 kms−1, 1–2 km) with a large wavespeed gradient, and relatively homogeneous layer 3 (6.0–6.8 kms−1, 5 km) is found on the oceanic side of the trench. Observations of shear waves converted at the boundary between the sedimentary layer and layer 2 gave compressional to shear wavespeed ratios of about 7.0 for the topmost sedimentary layer and 1.73–1.77 for layers 2 and 3. The transition of structure occurs slightly landward of the trench axis and thick low wavespeed materials (P wavespeed of 2.5–4.7 km s−1) persist beneath the continental slope. The density profile derived from our wavespeed structure is consistent with published free-air gravity anomaly data. The general crustal structure in the southern part of the Kurile Trench is similar to that of the Japan Trench off Sanriku. However, the distribution of the thick low wavespeed materials on the continent side differs between the two trench regions. These materials are more abundant in the Kurile Trench region, as is also inferred from the gravity anomaly pattern. The variability of the gravity anomaly on the continental side along the trench axis suggests that the distribution of these materials changes even within a single trench system. The seismic activity inferred from S–P time distribution at each OBS is high near the trench, and low in the oceanic basin beyond about 30 km from the trench axis as well as on the continental side where thick low wavespeed materials exist. An activity which seems to occur exactly in the narrow transition zone dividing the typical oceanic crust and the thick low wavespeed materials in the continental side structure is found.

Stratigraphy and geology of the Neogene Atsunai Group of the Atsunai and Urahoro areas in southeastern Hokkaido, Northern Japan

Stratigraphy and geology of the Neogene Atsunai Group of the Atsunai and Urahoro areas in southeastern Hokkaido, Northern Japan

An Unusual Case of Aggression by a Fish-owl

On May 31st 1986, while observing a pair of Blakiston's Fish Owls (Ketupa blakistoni) in their breeding territory, I witnessed a unique encounter between the male owl and a Black-crowned Night Heron (Nycticorax nycticorax). The Black-crowned Night Heron is very rare in Hokkaido. It does not breed there (WBSJ, 1981), and in fact was not recorded there at all by WBSJ (1982), although OSJ (1974) does mention records from that prefecture. The early summer of 1986 saw an unprecedented invasion of herons and egrets of several species in southeastern Hokkaido (Brazil, in press) and clearly a single night heron arrived during this influx. Since, in Japan, the fish owl is confined to the island of Hokkaido, and now mostly to the eastern third, it is highly unlikely that these two species have encountered each other in this country before. The ranges of the two species do not overlap in the Soviet Union either (Flint et al., 1984).

Shape and size of Japanese sardine school in the waters off the southeastern Hokkaido on the basis of acoustic and aerial surveys.

Acoustic and aerial survey was carried out during 1981-1983 in the area where a big catch of sardine Sardinops melanosticta has been taken. From the echo sounder survey, sardine schools keep at a depth between 10-20m (sometimes even deeper) during day time and the size of most sardine schools ranged between 10 and 20m. On the other hand, the longest sardine school dimensions ranged mainly from 20-40m and more than 100m was scarcely observed by the scanning sonar survey. During aerial survey, more than 293 schools were easily observed and identified because sardine swam in the shallower layer described above. On the contrary, the horizontal dimensions of school ranged mainly from 20-200m during the aerial survey. These values taken from the acoustic and aerial survey were different. The difference may be caused by the avoidance of the ship. The aerial survey technique is effective to study fish schools in nature when the fish commonly migrate to the near-surface. Although the efficiency of the aerial survey was seen, it is necessary to make synchronized air-and ship-borne observations in future.

A Remarkable Fall of Migrant Passerines on the Ship

On 19-20 October, 1980, we kept bird watching on the Marimo (9000t), a ferry-boat of Kinkaiyusen Co., from Kushiro, southeastern Hokkaido, for Ariake pier, Tokyo port. On 19 October, 1980, at 12:30 hours, the Marimo left Kushiro in the rain and haze. At about 13:10 hours, the weather changed. The ship was surrounded by a dense fog and fine rain and went on a calm sea at the speed of 20 knots. At 13:10 hours, we began to watch the birds as usual. After ten minutes, we heard the calls of many thrushes and buntings flying overhead in the dense fog. They were probably flying some hundred meters above the water, but we could not find out them. At 13:25 hours, throughout the dense fog, some of them began to fall on the ship in groups. The flights continued until 13:55 hours and headed between SW and W. From 13:25 to 13:45 hours, seventy birds of sixteen species fell on the deck. The position of the ship was 42°54'N, 144°15'E at 13:10 hours and 42°40'N, 144°05'E at 14:00 hours; these positions were about 10-21km from the nearest coast. Between 13:55 hours and evening, no calls were heard and no flights were observed. The fallen birds had damped feathers, and most of them were apparently exhausted. At first they alighted on the upper, middle and lower decks. Then, after two hours, they gathered on the lower deck and adjecent garage to take shelter from winds and rain. We kept watching and gave them avairable food, such as crumbs of potato croquettes, biscuits, sembei (Japanese rice biscuits) and rice. Soon the thrushes and buntings fed these foods, and on 20 October the bramblings joined them. On 20 October, when we began watching at 7:00 hours, we found new comers settled on the lower deck. We estimated that twelve birds of seven species had alighted on the ship during the previous night or in the early morning. About a half of birds fallen on the ship died. These were exhausted buntings and insectivores. Judging from the weather conditions of 18-20 October in their northern breeding areas, it seems that these birds started southward in better weather, but encountered with an unexpected rainy zone which was extending northward. Furthermore, the dense fog caused by a prevailing warm front, must obstruct their course.

Aseismic faulting following the 1973 Nemuro-oki earthquake, Hokkaido, Japan (a retrospective study)

Tidal records at Hanasaki, southeastern Hokkaido, are analysed to clarify the post-seismic crustal vertical movement in the 1973 Nemuro-oki, Japan, earthquake. The result shows that the post-seismic uplift, as speculated byKasahara (1975), terminated in late 1975 and reverted to the previous rate of rapid subsidence of about 1 cm/yr. Ceasing of the post-seismic uplift, which occurred much earlier than previously speculated, could be explained by supplementary mechanisms, such as frictional resistance against creeping at the fault surface. This unexpected mode of movement, however, raises a new question about the accumulation of tectonic movements in this district. Since the subsidence rate extrapolated from geomorphological data for the past several thousand years is almost one order of magnitude lower than the recent rate as mentioned above, we have to provide some alternative explanation for the discrepancy between the two rates. In other words, simple repetition of co-, post- and inter-seismic movements in seismic cycles due to plate subduction, must be modified in this district. Several possible modifications to the subduction process are suggested, and a brief discussion of vertical movements expected in each case is given.

Birds of Tokachi District, Hokkaido

Surveys on birds were carried out in four types of habitats, deciduous broad-leaved forests, young conifer plantations, cultivated fields and residential areas at Shintoku, Tokachi District, south-eastern Hokkaido from 1976 to 1979.A total of 76 species of birds were recorded in the study areas. Of them Charadrius placidus was recorded for the first time from Tokachi District.In the deciduous forest of Shintoku-yama 60 species of birds were observed. Dominant species were Phylloscopus occipitalis, Ficedula narcissina, Parus palustris and P. major in summer and were Parus palustris, Sitta europaea, Pyrrhula pyrrhula and Corvus macrorhynchos in winter. The avifauna of the deciduous forest along the Sahoro River was similar to that of the forest of Shintoku-yama. In young conifer plantations 17 species of birds were found in summer. Lanius bucephalus, Emberiza cioides and Uragus sibiricus were dominant species there. The avifauna was remarkably poor in comparison to that of deciduous forests above mentioned. In the cultivated field 30 species of birds including some forest birds were observed because of presence of woods and shelter-belts in the area. Passer montanus was the most abundant, and then Streptopelia orientalis, Emberiza spodocephala and Corvus corone were dominant species. In the residential areas only Passer montanus was dominant.There was a tendency that the species diversity was high in deciduous forest, and was low in young plantations and the residential areas.

PREVAILING WINDS IN THE KONSEN-GENYA, SOUTHEASTERN HOKKAIDO

In this study, the distributions of the direction and velocity of the prevailing winds in Konsen-Genya, Southeastern Hokkaido, were made clear by using results of field observation and available wind data. First, investigations were carried out on the distribution of prevailing wind directions and wind velocity observed at fourteen agrometeorological stations in Konsen-Genya. Secondly, field observation were made on wind-shaped trees in order to make clear the detailed distribution of the prevailing winds and local wind conditions. The grade of defor-mation and the direction of deformation of wind-shaped larch trees (Larix leptolepis) were measured at about 100 points in August, 1972. The results obtained in this study are summarized as follows: In summer: (1) The southerly winds from the Pacific Ocean blow up to north along the Kushiro river. (2) The southerly winds from the Pacific Ocean blow up to north in the central part of the Konsen-Genya, and then gradually change the direction northeastwards along the Shibetsu mountains and one branch of the southerly winds flows northwestwards from the Nemuro Bay. (3) The easterly winds from the Nemuro Bay blow into the lowland along the Shibetsu and the Nishibetsu Rivers. Their easterly border runs on the eastern side of the Kenebetsu, Nishishunbetsu and Chanai regions. (4) The strongest wind region is found on the coast and the weak wind prevails in the Shibecha, Arekinai and Ota regions. In winter: (1) The northerly winds blow from the Sea of Okhotsk to Pacific Ocean on the lowland area along the Kushiro River. (2) One branch of the northerly winds blows southeastwards between the Nishibetsu moun-tains and the Shibetsu mountains. (3) The westerly winds blow from the Kenebetsu and Nishishunbetsu regions to the Nemuro Bay. (4) The strongest wind region is found in the lowland along the Kushiro River as well as in the Shibetsu region. The border of the region with strong prevailing winds estimated from wind-shaped trees in winter runs in the Nishibetsu and Nishishunbetsu regions. Further, an attempt was made to clarify the relation between the mean wind velocity of the prevailing wind in summer at the thirteen agrometeorological stations and the grade of wind-shaped trees of Larix leptolepis in the Ishikari Plain, the Shari-Abashiri region and Konsen-Genya. The result is represented by the following equation: Ws=1.6+0.95 Gsl where, Ws: mean wind velocity (m/s) observed at the meteorological stations in summer, and Gsl: grade of wind-shaped trees of Larix leptolepis in summer. This means that the mean wind velocity in summer (m/s) is approximately equal to the value adding 1.4_??_1.6 to the grade value of wind-shaped larch tree.

The Movement of the Japanese and the Ezo (A-inu) Settlements in South-eastern Hokkaido

During the pre Meiji Period, Hokkaido was the area where contact between the Japanese and the Ezo (A-inu) took place. History shows that the Japanese enjoyed an expansion of their power through this contact while the Ezo people declined in strength.The history of the advance of the Japanese and the retreat of the Ezo is well reflected in the moves of these two races.These movements can be classified into two main movements. In the first place, the Japanese established a base in the southern part of Oshima Peninsula and gradually widened their territory. The Ezo, on the other hand, receded toward the north. Secondly, in propotion to the tendency of the Ezo being controlled economically by the Japanese, the Ezo gradually moved from the mountainous area to the sea side and concentrated their settlements in places advantageous for contact.This paper is an attempt to clasify to what extent these movments had taken place by the first half of the Bunka period (1804-17) and to show the subsequent regional differences brought about in these changes.As a result, south eastern Hokkaido can be classified as follows:1. South of “Nodaoi” was the settlement of the Japanese. Very few Ezo lived in this region and Japanese villages were located continously along this coast.2. In the area between “Yamakoshinai” and “Shiraoi” were the coastal villages of the Ezo which were predominantly the “Kyosei Buraku” (Proscribed Villages). Ninety-seven per cent of the total villages were located on the coast and the average number of houses per village was sixteen.3. The entire area of coast forming Uchiura bay between the area 1. and 2. were settled by both Japanese and Ezo.4. In the area between “Yufutsu” and “Kushiro” Ezo villages were located along the river. This area has a heavy predominance of “Shizen Buraku” (Free villages). In the western part of this area where the number can be counted clearly, ninety per cent of the total villages were located along the river, and the average number of the houses per village was seven.5. In the area between “Akkeshi” and “Nemuro” there were Ezo coastal villages which were predominantly the “Shizen Buraku”. [footnote] “Kyosei Buraku” (Proscribed Villages)……Villages in which the Ezo were compelled to live by the Japanese.“Shizen Buraku” (Free Villages)……Villages in which the Ezo prefered to live.

Geology and ore deposits of the Shakotan Peninsula, southeastern Hokkaido (II)

A dome structure formed of successive pyroclastic accumlation of so-called “green tuff effusion” is the main geologic constituent of the Shakotan Peninsula, southwestern Hokkaido. Igneous effusion and intrusion held in the district are carried wholly concordant to this dome structure; intrusive bodies are prefered to the central part of the dome and younger effusives are arranged to the peripheral part. Further, prominent mineralized zones closely allied to this geologic structure are known in this volcanic field. They are arranged to the cross direction of the axis of the peninsula. With them, interesting zonal distribution of ore deposits such arrangement as (1) Mn (Pb, Zn) deposits disposed to the central part of the dome succeeded by (2)|Cu, Pb, Zn (Au, Ag) deposits, (3) FeS2 deposits, and (4) BaSO4 deposits to the outer parts, are well ascertained. Of these deposits, some peculiar features of ore mineral are mentioned. They are unusual occurrences of pyrrhotite and molybdenite in the (1) Mn (Pb, Zn) deposits, realgar and orpiment in the (2) Cu, Pb, Zn) (Au, Ag) deposits and stibnite in the (4) BaSO4 deposits. The trace elements associated with these deposits have also peculiar behaviours. High concentration of W in the rhodochrosite from the (1) Mn (Pb, Zn) deposits, and Bi, Mo, Sn in the sulphide minerals from the (2) Cu, Pb, Zn (Au, Ag) deposits are their prominent features. Several varieties of wall rock alteration are mentioned with these ore deposits. Although sezicite-quartz and montmorillonite-kaolinite-quartz associations are the common feature of wall rock alteration of them, carbon-itization around the (1) Mn (Pb, Zn) deposits, occurrence of alunite, diaspore or jarosite with the (3) FeS2 deposits and the (4) BaSO4 deposits are the peculiar feature of this ore field. Their peculiarity is well serve for the prospecting researches.