Lake Izunuma Research Articles

Size-dependent ontogenetic diet shifts to piscivory documented from stable isotope analyses in an introduced population of largemouth bass

Piscivorous largemouth bass (Micropterus salmoides) have been introduced in several regions outside of their native range in North America, resulting in significant disturbance to native fish communities. This species exhibits an ontogenetic diet shift from zooplanktivory to piscivory as juveniles. An early switch to piscivory allows 0+ bass to increase their growth rate prior to winter, resulting in reduced mortality. However, little is known about the dietary switch at the population level during the first year. We used carbon stable isotope analyses to examine the diets of age 0+ individuals in Lake Izunuma, Japan. The onset of the shift to piscivory occurred at a smaller size than in native or other non-native areas [>40 mm total length (TL)]. We found a positive correlation between TL and δ13C throughout summer and autumn. Small individuals had δ13C values that were similar to those of zooplankton, whereas large individuals had δ13C values that were similar to those of cyprinid prey species. This suggests that the smaller 0+ individuals remain zooplanktivorous until late autumn, whereas the larger individuals shift to piscivory as early as June, soon after the breeding season ends. Our results also suggest that a significant number of 0+ bass failed to switch to piscivory until the winter of their first year, despite the smaller size threshold for the onset of piscivory.

First record of the White-breasted Waterhen Amaurornis phoenicurus in Lake Izunuma, Miyagi Prefecture, Japan.

First record of the White-breasted Waterhen <i>Amaurornis phoenicurus</i> in Lake Izunuma, Miyagi Prefecture, Japan.

伊豆沼のヒシの栄養塩吸収・溶脱特性を利用した栄養塩濃度制御方法の提案

The floating-leaved plant Trapa japonica, one of the abundant aquatic plants in Lake Izunuma, was used for nutrient uptake and release tests. By comparing the nutrient elution rates from the sediment and the nutrient uptake rates by Trapa japonica, it was estimated that in Lake Izunuma the Trapa japonica communities could take up most of the nutrients eluted from the sediment during summer. It was also confirmed that NH4-N released from Trapa japonica changed to NO3-N via NO2-N. This result was quite similar to the NH4-N, NO2-N and NO3-N concentration changes in Lake Izunuma from autumn to winter. In Lake Izunuma, the dissolved inorganic nitrogen concentration was high in autumn and winter. On the basis of the results of the discharge experiment to determine the effect of the reduction in the water level by tilting the water gate of Lake Izunuma, we consider that the nutrients released by the aquatic plant from autumn to winter can be removed effectively by this water level reduction.

Plants of genus Azolla (Azollaceae) newly recorded from Lake Izunuma

Plants of genus <i>Azolla</i> (Azollaceae) newly recorded from Lake Izunuma

Changes in the trophic state and the benthic fauna in Lake Izunuma, with special reference to the chironomid species

Changes in the trophic state and the benthic fauna in Lake Izunuma, with special reference to the chironomid species

Records of aquatic oligochaetes (Annelida, Clitellata) from Lake Izunuma and Kabukurinuma Marsh, Miyagi Prefecture, northern Japan

Records of aquatic oligochaetes (Annelida, Clitellata) from Lake Izunuma and Kabukurinuma Marsh, Miyagi Prefecture, northern Japan

Searching for spawning areas of Micropterus salmoides by Side scan sonar and inspecting the validity of this method in Lake Izunuma

Searching for spawning areas of <i>Micropterus salmoides</i> by Side scan sonar and inspecting the validity of this method in Lake Izunuma

Surveillance of Avian Influenza Viruses in Northern Pintails (Anas acuta) in Tohoku District, Japan

Among winter migratory waterfowl, Northern pintails (Anas acuta), in one of the largest flocks in Tohoku district, northeast Japan, were surveyed for influenza A viruses at five wintering sites in three prefectures, viz., Aomori, Akita, and Miyagi. A total of 38 influenza A viruses were isolated from 2066 fecal samples collected during November 2006 through March 2007. The overall isolation rate was 1.84%. Eleven different subtypes were isolated, including nine H5N2, seven H6N8, seven H10N1, four H4N6, three H6N1, three H11N9, and one each of H1N1, H6N2, H6N5, H10N9, H11N1. Only the H4N6 subtype was detected during two successive months, November and December, from Lake Ogawara of Aomori prefecture. One wintering site, Lake Izunuma of Miyagi prefecture, was negative for virus isolation throughout the study period. During the sampling period, the highest virus isolation rate was in December (4.90%) followed by November (2.18%), January (0.91%), and February (0.30%). Virus isolation was negative for samples collected in March 2007. These results suggest that influenza viruses are introduced by Northern pintail when they migrate into Japan, but the viruses are not maintained in the flocks, most likely because the birds are not breeding during the winter. We believe that this relatively large data set creates a strong foundation for future studies of avian influenza virus (AIV) prevalence, evolution, and ecology in wintering sites, along with the role of Northern pintails in the spread of AIV during their migration from northern Russia and Asia to Japan.

Effects of climatic conditions on the northward expansion of the wintering range of the Greater White-fronted Goose in Japan

The Greater White-fronted Goose Anser albifrons has recently begun to winter at Lake Otomonuma (Akita Prefecture), a migratory stop-over site located 180 km northwest of its main wintering site at Lake Izunuma–Uchinuma (Miyagi Prefecture), in northern Honshu, Japan. Data collected over a 17-year period (from 1987/1988 to 2003/2004) have allowed us to analyze factors influencing the large-scale redistribution of this species. The number of geese in Akita increased during November and December, but decreased in January. The number of geese wintering in Akita from November to December was not correlated with the number wintering in Miyagi; therefore, migration from the breeding area or from northern staging sites seems to have caused the population to increase in Akita in December. The population in Akita decreases with low temperatures in January; however, the decrease in Akita was not correlated directly with an increase in Miyagi from December to January as the geese also visit other more southerly areas in addition to Miyagi. In fact, we found no significant correlation between the size of the goose population in Akita and climatic conditions during November and December. Our analysis demonstrated that the use of Akita by Greater White-fronted Goose in winter was attributed to density-independent effects regardless of the population fluctuation in Miyagi from November to December, and to severe weather conditions in January forcing the geese to move from Akita to a southern refuge.

Effects of flooding on a wetland bird community

The Lake Izunuma–Uchinuma was extensively flooded in 1998 and vast areas (approximately 200 ha) of rice fields were submerged for the first time since the land was reclaimed in 1963. When the numbers of birds in 1998 were compared with those in normal years (1995–1997), the numbers of black‐crowned night herons (Nycticorax nycticorax L.), cattle egrets (Bubulcus ibis L.) and black kites (Milvus migrans Boddaert) increased during the flooding, and the numbers of ducks, especially dabbling ducks (seven species of 11 Anas spp.) were high even after the flooding, while the numbers of the little grebe Tachybaputus ruficollis Pallas were diminished by the flooding.

Interaction between homoacetogens and methanogens in lake sediments

The interaction between homoacetogens and methanogens in lake sediments was investigated using hydrogen consumption as an indicator. Sediments samples were obtained from Lake Izunuma, Miyagi prefecture, Japan, a wintering place for migratory birds from Siberia. A batch experiment using H 2 CO 2 as a substrate was conducted to determine the acetate generation and methane production potential of the sediments. Incubation for 4 d at 37°C gave the following stoichiometric equation: 88H 2 + 39HCO 3 − + 22H + → 17CH 3COO − + 5CH 4 + 83H 2O. The activities, ν m, of hydrogen-utilizing homoacetogens and methanogens respectively ranged from 3.2 to 48 and from 1.8 to 3.2 mgCOD·gVSS −1·h −1. The population of hydrogen-utilizing homoacetogens was determined to be 2.6 × 10 8 MPN·gVSS −1, which was approximately two orders of magnitude higher than that of hydrogen-utilizing methanogens. The results suggest that homoacetogens in the sediments functioned not only as hydrogen consumers but also as major degraders of organic matter, forming acetate as the major reduction product.

Wintering Ecology of White-fronted Geese Anser albif cons in Paddy Fields on the Northeast of Lake Izunuma in Spring Migration Season

Wintering Ecology of White-fronted Geese Anser albif cons in Paddy Fields on the Northeast of Lake Izunuma in Spring Migration Season

伊豆沼に設置された給餌地システムの汚濁負荷削減効果についての調査研究 （第３報）

伊豆沼に設置された給餌地システムの汚濁負荷削減効果についての調査研究 （第３報）

伊豆沼に設置された給餌地システムの汚濁負荷削減効果についての調査研究 （第２報）

Lake Izunuma is a famous place for the coming of migrating flying swans. But, the leftovers of foods which were fed to the waterbirds and their droppings are one of the causes of water pollution.In order to prevent water pollution of Lake Izunuma, a feeding place system was constructed near the lake. It was reported in the previous reports that a build-up of pollutants were found in the feeding pond and the purification rates of 0.13 mg/l/day COD, 1.05×10-2 mg/l/day T-N and 0.53×10-3 mg/l/day T-P were obtained in a plant, Zizania latifolia, field (constructedwetland).In this paper, the results which obtained in the second year study were reported and as follows.1. The purification rates of 1.2-1.3×10-2 mg/l/day T-N and 0.68-1.03×10-3 mg/l/day T-P were obtained in a plant field (constructed wetland). These were larger than those of first year. These will be caused by the larger growth of the plant. On the other hand, the purification rate of COD was almost same to that of first year.2. The unit loading factors of 5.30 g/swan-day T-COD, and 0.49 g/swan-day T-TN due to the coming of migrating flying swans were obtained.

伊豆沼に設置された給餌地の汚濁負荷削減効果についての調査研究

Lake Izunuma is a famous place for the coming of migrating flying swans. But, the leftovers of foods which were fed to the waterbirds and their droppings are one of the causes of water pollution.In order to prevent water pollution of Lake Izunuma, a feeding pond was constructed near the lake. Last winter, a total number of about 160, 000 waterbirds entered into this pond anda build-up of pollutants of 12kg T-N, 1.5kg T-P and 120kg COD were found. This means that the pollutants going to Lake Izunuma were reduced.After this, the polluted water in the feeding pond will be introduced into a plant field and purification by the plant, Zizania latifolia, which is a food for the swans, will be attempted.

Notes on the migration route of the White-fronted Geese Anser albifrons wintering at Lake Izunuma

Lake Izunuma, Miyagi Pref., has the largest population of geese wintering in Japan. On 8 October 1980 we found a juvenile Swan Goose Anser cygnoides at the lake in a flock of White-fronted Geese (Fig. 1). This bird, the sole Swan Goose recorded in the winter of 1980-81 in Japan, was always observed together with White-fronted Geese. We followed up the Swan Goose, as a marker of the movement of the Izunuma White-fronts, during the northbound migration. It took the course from Lake Izunuma to Hachiro-gata in Akita Pref. (observed 13 March 1981) and then to Seika-ko in Hokkaido (observed 8 April to 5 May 1981) (Fig. 2). The route thus brought out is a second northbound migration course of the Izunuma White-fronted Geese, the main route being the course from Lake Izunuma to Hachiro-gate and then to Ishikari Plain in Hokkaido (Fig. 3).

Studies on the Behavior of Wintering Geese

(1) White-fronted (numbered 6, 000 in 1978) and Bean geese (numbered 1, 500 in 1978) winter in Lake Izunuma in Miyagi Prefecture. Lake Izunuma is now the only roosting place of geese on the Pacific coast of Japan. The authors studied the distribution of feeding area of the geese wintering at Lake Izumuna for eight years from 1971 to 1978. These geese feed chiefly in harvested paddy fields. This feeding habit is in contrast to that in England or other European countries where geese feed in arable lands and grasslands. (2) In ordinary years the feeding areas of the geese at Lake Izunuma is limited to the alluvial plains in northern half of Miyagi Prefecture. In years of heavy snow, however, they move to the areas with light snow for feeding, south to the southern part of Miyagi Pref. and the northern part of Fukushima Pref., sometimes reaching to the Kanto Plain which is three hundred kilometers south of Lake Izunuma. (3) The past history of decrease of the geese populations in Japan accounts for the present situation of the geese whose feeding areas are restricted to the Senpoku Plain in northern Miyagi Prefecture. Due to heavy hunting and gradual worsening of environments since the Imperial Restoration of Meiji, geese in Japan have lost their wintering grounds one by one from Kyushu to Kanto, namely from the south to the north, and today the Senpoku Plain has left as the last remained wintering place of geese on the Pacific coast of Japan. (4) The Feeding areas of White-fronted Geese and those of Bean Geese in the Senpoku Plain are separated topographically with each other. The feeding areas of White-fronted Geese are situated in the northern and the western parts of the Senpoku Plain and they are distributed along the middle to the upper reaches of the Hazama and the Naruse rivers. Bean Geese feed in the eastern and the southern parts of the Senpoku Plain, in which the feeding areas are located along the middle and the lower reaches of the Hazama, Naruse and Yoshida rivers. The two species were occasionally seen feeding together in the same field in a few districts, but such is rather rare.However, in the years of heavy snow and when the geese migrated to the south, they were more frequently observed to feed in mixed flocks. (5) The spatial separation of feeding areas of the two species may be due to their former habitats in their history, that is a habitual attachment for the former feeding sites ('traditional attachment'). The feeding areas of Bean Geese before the reclaim for fields are presumed to have been a vast marsh area, where the Been Geese could obtain water-chestnuts (Tarapa Linn.) and other aquatic plants. Water-chestnuts are growing over in marshes and must be a 'traditional diet' of Bean Geese in Japan.The reclaimed paddy fields supply a fairly good amount of paddy gleans for geese so that they still hold the habitual attachment to the places of the former feeding areas. In the case of White-fronted Geese, the 'traditional attachment' is also the main factor for separation of feeding areas from Bean Geese and the aquatic plant Makomo (Zizania Linn.) is supposed to be one of their 'traditional diet' in Japan.

Studies on the Behavior of Wintering Geese

(1) The authors studied the population size and change of wild geese wintering and roosting at Lake Izunuma (Fig.1), Miyagi Pref., northern Honshu, for seven years from 1971 to 1977.Monthly counts of bird number were made at daybreak when flocks of geese fly out of Lake Izunuma to feeding places. In addition, the numbers of geese roosting at the lake or feeding at paddy fields were counted during the daytime 3 to 4 times a month.(2) The wintering geese at Lake Izunuma consist chiefly of the White-fronted Goose (Anser albifrons) and the Bean Goose (A. fabalis). The Lesser White-fronted Goose (A. erythropus), Lesser Snow Goose (A. caerulescens), Aleutian Canada Goose (Branta canadensis leucopareia) and Brent Goose (Branta bernicla) are rare or accidental visitors. In 1972 there were about 3, 000 White-fronted Geese and 200 Bean Geese. In spite of deterioration of the natural environment surrounding Lake Izunuma, they increased to 5, 600 and 1, 400 respectively in the following five years (Fig.4). The reason for the increase of the population of geese may be attributed to the prohibition of hunting of wild geese in Japan in 1971. (3) Seasonal changes of numbers of the wild geese wintering at Lake Izunuma were shown in Figs.3, 5 and 8. In these monthly-peak-number graphs, there are 'cap' and 'two-peak' types (Fig.3). The graph of cap type shows an ordinary pattern of population change of wild geese at Lake Izunuma during one wintering period, i.e., wintering geese arrive in a small number in late September, increase to a large number in October, reach to a peak number in November or December, begin to decrease in late January, and then depart in February or March. The graph of two-peak type indicates that wintering geese take a temporary refuge in the south when paddy fields are covered with thick snow for a period of 30 days or more. They returned to roost at Lake Izunuma when the snow in paddy fields melted.(4) The monthly-peak-number graphs of the White-fronted Goose resemble that of total wintering geese, because the number of White-fronted Geese is 60-80 % of the total goose number.On the contrary, the numbers of Bean Geese increases to a peak in October and then reaches at maximum in December. Against snow, Bean Geese also take refuge in the south but they seem to be more resistant to snow and the extent of movements during the snowy periods is smaller.(5) The wintering geese depart from Lake Izunuma in February or March regularly.In the year when there is not much snow, they usually leave in February and the monthly-peak-number graph becomes a cap type. When there is much snow, they leave in March and the monthly-peak-number graph resulted in a two-peak curve.

The migration course of geese wintering at Lake Izunuma (2)

The authors have been endevouring to survey the migration course in spring of the geese wintering at Lake Izunuma in Miyagi Prefecture, Northern Japan.1. Late in April 1975, we found flocks of wild geese on the Ishikari Plain in Hokkaido. The flocks consisted of approximately four thousand of White-fronted Geese (Anser albifrons frontaris Baird) and two Aleutian Canada Geese (Branta canadensis leucopareia (Brandt)).They roost at night on Ishikari Bay on Japan Sea coast, about thirty kilometer west of Ishikari Plain. On clear days, they feed on paddy fields of Ishikari Plain in the early morning and late afternoon, and return in the midday to Ishikari Bay. On cloudy or rainy days, however, the geese remain on fields longer, sometimes all day long.2. Judging from data, it seems that the flocks geese observed on Ishikari Plain are those which have migrated from Hachirogata in Akita Prefecture. The following table shows the number of geese on Hachirogata and Ishikari Plain and the relevant dates.a. Number, species and date.(Total number of geese at Hachirogata includes that of Bean Geese.)b. Aleutian Canada Goose.The Aleutian Canada Goose is a rare bird in Japan and only two have been found in 1975. The two Aleutian Canada Geese disappeared from Hachirogata with other geese in the middle April and reapeared on Ishikari Plain in the same season. They are considered to be identical.3. We may conclude that in spring the geese which have wintered at Lake Izunuma, may first migrate to the paddy fields of Hachirogata on their way to north and then arrive on Ishikari Plain for resting and feeding. They stay here till early May.

On the migration course of geese wintering at Lake Izunuma

The total number of wild geese migrating to Japan in recent years is estimated as about 6, 000-7, 000 and about two-thirds of them used to winter at Lake Izunuma, situated in the northern part of Miyagi Prefecture, Honshu.In January 1973. our bird census at Lake Izunuma revealed a flock of 3, 000 White-fronted Geese (Anser albifrons), 230 Bean Geese (Anser fabalis) and 3 Aleutian Canada Geese (Branta canadensis leucopareia (Brandt)). The majority of them had started from there to northward flight late in February. The junior author and Akio Watanabe observed early in March on paddy field at Hachirogata, about 2, 000 White-fronted Geese, 155 Bean Geese and 2 Aleutian Canada Geese. Hachirogata is located at the north-western part of Akita Prefecture, Tohoku district of Honshu, having an area of 22, 000 ha, and had been known as wildfowl resort since ancient days. Fifteen years ago, Hachirogata became reclaimed by drainage and now changed into large paddy fields.Our attention was directed to the appearance of Aleutian Canada Geese at Hachirogata. Since, the Aleutian Canada Goose is a rare bird, we concluded that the flocks of wild geese accompanied by 3 Aleutian Canada Geese had migrated from Lake Izunuma to Hachirogata on the way of north ward migration.Next year in 1974 we noticed the same phenomena, as listed below:Observed at Lake Izunuma Jan. Mar. 1974 (Most abundant number) White-fronted Goose … 4, 493 birds Bean Goose … 307 Aleutian Canada Goose … 2 Lesser Snow Goose … 1 Observed at Hachirogata Mar. Apr. 1974 (Most abundant number) … 3, 600 birds … 550 … 2 … 1The Lesser Snow Goose (Anser caerulescens caerulescens (L.)) is also a rare bird and one wintering individual of this bird was recorded at Lake Izunuma during winter of 1974. It disappeared from Lake Izunuma on 24th of March and found at Hachirogata on 28th of the same month.The straight distance from Lake Izunuma to Hachirogata is about 170km and between the two places there are Oh-u mountain range and Mt. Kurikoma (1, 628m above the sea). In order to veryfy our presumption that wild geese fly along this straight line crossing over Oh-u mountain range to Hachirogata, we tried to obtain the informations by questionnaire to the villagers, farmers and hunters living beneath this flyway, whether they had seen wild geese passing high overhead on their way. We have collected 20 evidences that have witnessed passing wild geese within a period from autumn 1973 to spring 1974, and 29 persons answered that they had sighted during last sixty years passing flocks of wild geese high up in the sky.The migration course of wild geese has been hitherto supposed to be: (1) from Hokkaido southwards to Honshu, (2) across the Japan Sea to coastal prefectures in Japan, (3) along the Korean Peninsula to western Japan. Among them the first route, namely from Hokkaido to Honshu, is divided into two ways at Tohoku district (North-East District of Honshu), one way of which goes southward along the Pacific Ocean coast, and the other along Japan Sea coast, thus the the two ways run parallel and never meeting each other.But, we have added a crossing flyway from Pacific coast resort at Lake Izunuma to Hachirogata on Japan Sea coast, passing over Oh-u mountain range lying between them.