The field survey conducted at Lake Biwa showed that the vegetation area of submerged macrophytes increased by 15% in North Lake in 2002, 73% in South Lake and 36% overall in comparison with that of 1997. During the growth period of the submerged macrophytes in 2002, the water level of Lake Biwa was 50 cm lower than in 1997, and the vertical distribution of vegetation area of submerged macropytes also shifted 50 cm deeper. In South Lake, in addition to the shift of vegetation area, the area size at the same water level significantly expanded. Increased light availability due to decreased water level expanded the vegetation area of the submerged macrophytes during the growth period. There are signs of positive feedback that the clarity of water transparency becomes better as the number of submerged macrophytes increases.

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Upper tidal river area is very important for maintaining population of the Japanese mitten crab Eriocheir japonica, because megalopa larvae settle and metamorphose to the crab stage in this area. I investigated the preference of environmental condition of the megalopa and young crabs of E. japonica by the field experiment in this area. Artificial grass mats (30 cm × 30 cm × 1.5 cm) with three coverage types (stone 25%, stone 75% and stone + reed vegetation 75%) were set in 11 sites in the upper tidal river area of the Saigo River, Fukuoka Prefecture, Japan. Settlement of megalopa concentrated in the rapid flow area right below the fishway, suggesting the positive rheotaxis of megalopa. Thus it was presumed that presence of weir and fishway within tidal river area strongly influences the distribution pattern of young crabs. Young crabs after metamorphosis tended to disperse from the settlement area to the surroundings as they grew larger. Density of crabs was higher under the presence of reed vegetation in the flat flow or pool areas, suggesting that reed vegetation was useful for the nursery ground of young E. japonica. The present result also showed that the method using the artificial grass mats was effective for the survey of E. japonica population.

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The identification of forest areas that are the sufficient sources of leaf-litter to streams is an important issue in riparian management, because leaf-litter is one of the most important foods for stream invertebrates. We monitored the leaf dispersal of two isolated chestnut trees in a deciduous forest on different sides of the stream, and then we verified the applicability of a simple physical model (modified Greene & Johnson (1989)’s model) to this actual data to predict leaf dispersal. The chestnut leaves were dispersed to about 25 m from the source trees, but most of the leaves fell within 15 m. The model predictions were consistent well with the observed results for the one tree, except for the vicinity of the source tree. Although the cumulative curves of the predicted leaf density were slightly lower than those of the observed leaf density, both the cumulative densities reached about 90% at 15 m from the source tree. We considerded that the model can estimate leaf dispersal with enough accurately when the wind regime is measured properly. Heterogeneous wind distribution in a riparian stand may impede accurate estimation of dispersal, but wind observation at a typical place in the stand is enough to get a rough estimation of leaf dispersal. Underestimation of leaf density near the source tree is not important problem for the purpose of this study. We are sure that this model is useful for estimating source distances of leaf-litter to stream in various types of riparian forests, although the model verification is insufficient.

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This report introduced the restoration project in the City of Bothell, Washington State, U. S. The construction of the new university campus in Bothell required mitigation. The Washington State Government, the proponent of the project, determined to restore the entire wetland ecosystem, which went beyond the mitigation. The hydrogeomorphic (HGM) approach to assessing wetland functions was applied to the project and the reference site was identified to define the wetland functions. The impact assessment, restoration design, monitoring protocol and contingency measures were developed based on the wetland functions. The restoration design was developed based on the wetland functions, and the new channel system design, placement of woody debris, and planting plan were determined. Construction was composed of grading, planting, and weed control. Maintenance and monitoring program based on the restoration design were undertaken after the construction. The University of Washington is responsible for the management of the restoration site after the construction. They developed guidelines to manage the site and utilize it for education, research, and nature study.

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[in Japanese]

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[in Japanese]

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We examined electrofishing catchability of six most abundant fish species in experimental stream A in the Aqua Restoration Research Center in Gifu, Japan. The electrofishing catchability can be defined as the total catch obtained by electrofishing divided by the sum of catches obtained by electrofishing and by chasing into D-shaped nets. The six species were classified into high catchability species (more than 80% of the catch) (Plecoglossus altivelis altivelis, Misgurnus anguillicaudatus, and Cobitis sp.) and low catchability species (less than 80% of the catch) (Zacco platypus, Gnathopogon elongatus elongatus, and Rhinogobius sp.). Two age groups were confirmed in each of the low catchability species by estimation of the fish size (total length mm). Each peak of the first and the second age groups were positioned less and more than 40 mm, respectively. The catchability of the first age group of Z. platypus as a swimming fish was significantly lower than the second age group of the species. The catchability range of Rhinogobius sp., a benthic fish, was lower (24%-67%) than that of Z. platypus and G. elongatus elongatus values. Furthermore, the catchability of the second age group of Rhinogobius sp. was lower than that of Z. platypus. These results suggest that electrofishing alone is not a suitable capture method because its capture rates for small swimming fish < 40 mm and for all sizes of benthic fishes are low. Therefore, electrofishing should be used along with the D-shape nets and the small swimming fishes and benthic fishes should be chased into the nets. Additionally, we recommend that further studies are required to determine not only the catchability for each of these species but also to study damages by electrofishing to fish under various voltage, pulse, and environmental conditions.

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In most developed countries, river restoration projects have rapidly increased since the 1990s. In this paper we reviewed river restoration projects around the world (with a main focus on European rivers), and discussed the social backgrounds of projects. Finally, we indicated future research needs for successful restoration. In Europe, recent flood damages and an advanced EU policy have fostered river restoration projects. In the US, diverse river restoration projects have been carried out and an excellent database of restoration projects was established. In Australia, the development of environmental flow guidelines was received top-priority. Based on international experiences of river restoration projects, we presented the following fundamental needs for Japanese restoration projects: (i) management of sediment and river channel dynamics, (ii) restoration of a dynamic flow regime, (iii) implementing scientific monitoring programs and river restoration database, (iv) implementing an ecological flood management.

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In planning habitat conservation, potential habitats should be evaluated by elucidating relationships between large-scale environment variables and the real distribution. Species - environment relationships on a broad scale are usually nonlinear and involve effects of interactions. Regression models are not capable for explaining such relationship and no standardized modeling method has been established. We, therefore, constructed a model for predicting potential distribution of forest green tree frog (Rhacophorus arboreus), by detecting thresholds of five environmental variables and applying them to a rule-based tree model. The five variables adapted for the model were forest cover, actual rainfall, maximum depth of snow, gradual slope area and annual maximum temperature. The accuracy of the model was higher when the effect of neighboring habitat was considered in the model (95%) than when it was not (75%). The result of randomized test shows that the model developed in this study is reasonably usable. The actual conservation status in local governments in Japan was evaluated through GAP analysis; comparing actually preserved areas with the potentially distributional areas. In the area along the Pacific-Ocean coast in Tohoku, Chubu and Kinki regions, habitats suitable for the tree frog are scattered and isolated, which requires well-planned and organized conservation effort. None of the local governments concerned, however, particularly Nara, Osaka and Wakayama Prefectures have no appropriate conservation policy. It is urgently required to establish measures for conservation in these prefectures.

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Based on a predictive habitat modelling approach, we investigated 1) the effects of damming on the distribution of salmonids and 2) whether the existing conservation areas for the salmonids are appropriate and effective in protecting their habitats in Hokkaido. A habitat model for masu salmon, one of the most commercially important species, predicted that their occurrence probability declined sharply approximately 30 years after damming. Areas where the probability had significantly dropped due to damming were distributed throughout Hokkaido. A habitat model for the Sakhalin taimen, a salmonid categorized as an endangered species, on the other hand, did not indicate a significant effect of damming on their occurrence, mainly because the taimen inhabit areas with low elevations where dams have not been commonly built. Thirty-two stream systems designated as conservation areas for salmonids by the government of Hokkaido had significantly higher levels of both occurrence probability and conservation value for masu salmon than the other stream systems in the island, but that was not the case for the Sakhalin taimen, indicating an inappropriate placing of conservation areas for this species.

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Salt marsh has become one of the most seriously altered ecosystems, and many species have been threatened in Japan. Developing simple and reasonable methods for predicting and evaluating ecosystem change is required for conserving and restoring wildlife of salt marshes. Physical characteristics of the habitat, in terms of elevation and sediment size, are identified in relation to salt marsh plant communities developed on and around a gravel bar in the Naka River, Shikoku, Japan. Maps of vegetation, elevation and sediment types were made through field surveys with an aid of aerial photographs in 2002 and 2004. Using GIS, the maps were overlaid to evaluate the characteristics of the habitat favored by each plant community and to compare the temporal change. In 2002, salt marsh plant communities, those of Suaeda maritima, Limonium tetragonum, Aster tripolium, Zoysia sinica var. nipponica, Fimbristylis ferruginea var. sieboldii preferably occurred in an area lower than high-tide level. S. maritima community and L. tetragonum community favored the lowest area where the time inundated in salt water is long, while A. tripolium community favored high-tide area. It is considered from the literatures that the distribution pattern was formed through competitive process among plants. All of these plant communities favored gravel area rather than silt or sand areas. Gravel might act as protector for seeds and seedlings against removal by floods. The vegetation pattern represents a condition recovered from the large-scale flooding occurred in 1998. In 2004, almost all areas along main channel were severely eroded and plant communities were disappeared due to large-scale floods, while salt marsh plant communities distributed on an interior side of the bar, so-called “Wando”, were remained. Wando as a topographical unit has an important function as the refuge for salt marsh plants.

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