This paper aims to propose concrete measures for the conservation of the mud loach (Misgurnus anguillicaudatus) in Sado Island of Japan, associated with the reintroduction of Japanese crested ibis (Nipponia nippon) that has a predilection to feed on the loach. The field survey was conducted at 80 sites on 7 rivers in the island in August 2007 and March 2008, in which the loach density and the micro-scale environmental factors (water depth [WD], degree of aquatic vegetation [AV], degree of riparian forest [RF], current velocity [CV], mud river bed [MB], concreted river bed [CB], and river bed pebble size [PS]) of the habitats were surveyed. Additionally, the macro-scale factors (paddy fields area [PA] and reservoirs area [RA] within a specific buffer circle) were also obtained using GIS software. The analysis using GLM and AIC showed that the AV (positive), MV (positive), CB (negative) and RA (positive), and AV (positive), MV (positive) and PA (positive) effect the loach density in August and March, respectively, indicating that the loach preferred the less artificial habitat surrounded by the paddy fields. The potential maps of the loach density were drawn by adapting the models on the rivers in the island: The loach density was especially high in the Kuninaka Plain that situated at central region of the island in both August and March, indicating the region was priority area for the conservation of the loach. In conclusion, removal of concrete revetment in the habitats and improvement of creek networks between rivers and landscape elements (paddy field and reservoirs) in the Kuninaka Plain would be the effective conservation measurements for the loach.

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The effects of shrimp (Palaemon paucidens) on water quality and the zooplankton community were investigated by using eight enclosures in a restoration experiment pond of the Inbanuma Fishermen Cooperative Association in Kitasuga, Narita, Chiba (Japan). In shrimp enclosures, NH₄-N, total nitrogen (TN), and chlorophyll a (Chl a) concentrations increased soon after the start of the experiment, indicating shrimp excretion and bioturbation caused increased NH₄-N, TN, and Chl a concentrations. Suspended solids (SS), TN, total phosphorus (TP), Chl a, and dissolved organic carbon (DOC) were significantly higher (P < 0.001) when shrimp were present. The total density of cladocerans and rotifers decreased significantly when shrimp were present but increased in the absence of shrimp. Among cladocerans, total densities of Daphnia, Diaphanosoma, and Scapholeberis decreased significantly (P < 0.05) when shrimp were present; however, the densities of Alona and Chydorus, which are small-sized benthic animals, did not differ significantly in the presence or absence of shrimp. The results of this study show that the presence of shrimp decreased water quality because nutrient recycling was accelerated by shrimp excretion and bioturbation, in addition to the trophic cascade effects, i.e. zooplankton community structure changes from shrimp through feeding on large cladocerans.

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Spatial statistics was applied to the dataset collected in the Matsunase tidal flat in Mie Prefecture, Japan, in order to elucidate the effect of physico-biological factors that restrict spatial pattern of Manila clam, Ruditapes philippinarum, with spatial autocorrelation considered. Among 12 independent variables, the clam abundance was positively correlated with abundance of cyanobacterium (P < 0.05; partial Mantel test) and negatively correlated with ground elevation (P < 0.05), while diversity of macrofauna was marginally significant (P < 0.1). Faunal diversity was strongly correlated with ground elevation rather than the clam abundance. Manila clam was dominant in the study site and mainly lived in the offshore half of the intertidal zone. The upper margin of the clam habitat was close to the lower end of the swash bar. These results suggested that environmental factors relevant to ground elevation, i. e. extreme temperature and food insufficiency, could restrict vertical range of the clam habitat, inspiring what factor should be focused in future studies.

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Population genetic structure and migratory history of the common freshwater goby Rhinogobius sp. LD in the Shigenobu River system were surveyed by using three microsatellite loci and otolith Sr/Ca ratio, to examine effects of two types of dams, a single dam with a reservoir (Ishite-gawa Dam) and multiple erosion-control dams without reservoir. Genetic variabilities were high in the Shigenobu River populations and the estimated hetero zygosity ranged from 0.843 to 0.889. Considerable genetic differences were observed between populations above Ishite-gawa Dam (two sites) and populations of the other nine sites (above multiple erosion-control dams), within which the genetic heterogeneity was not observed. These results suggested that the populations above Ishite-gawa Dam were landlocked and differentiated genetically by the dam, whereas the goby populations were not isolated by multiple erosion-control dams. This was supported by the otolith Sr/Ca analysis, which indicated that the goby individuals sampled from the sites above the Ishitegawa Dam had not experienced saltwater whereas those above multiple erosion-control dams had experienced. In addition, Sr/Ca analysis suggested that a population just below the Ishitegawa Dam consisted of both landlocked (drifted from the reservoir) and sea-migratory individuals.

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This paper addresses the management of riparian forests (RF) in the natural levee zones of Hokkaido, based on the relationship between river channel configuration and RF dynamics before and after river improvement. Flow disturbances affect RF dynamics. The distribution of RF reflects river channel form longitudinally and micro-topography transversely. In an RF before improvement, intermediate, post-pioneer species predominate, mainly because the intervals between RF destruction are long for a meandering channel, whose flow changes more slowly than for a braided channel. Pioneer species grow on recently deposited sediment, and such species affect the microtopography by increasing the channel elevation through sediment capture, which promotes the establishment of replacement species and protects the RF. The seedlings of post-pioneer species that can adapt to environmental changes become canopy trees. After river improvement, most RF species are willows, which are not post-pioneer species. The extent to which willows dominate depends on the extent to which the channel floods, which in turn depends on the transverse elevation of the channel. It is thought that after river improvement, an RF cannot reach transition because of frequent natural and artificial disturbances (blowdown removal, river channel improvement, etc.) and land development near the channel. Because of such disturbances, fewer seeds of post-pioneer species are supplied from surrounding forest. This paper points out that natural levee zones do not have a system for restoring RF through flow disturbance, and it suggests that RF at different growth stages in natural levee zones is restored very little, even when the floodplain and meander channel are restored. Toward restoring RF dynamics that correspond to flow disturbances, we propose a river management method that allows the seedlings of post-pioneer species to establish among pioneer species in RFs where transition of vegetation is possible, and that allows the channel to migrate transversely.

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[in Japanese]

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Three months have passed since the Great East Japan Earthquake occurred. Public infrastructures were largely destroyed by the extreme tsunami. In these affected areas, it is reasonable to consider the grand design of the new land use and public infrastructure rather than restoring to the original state from the viewpoint of disaster prevention. In reconstruction from the Tohoku earthquake, the rehabilitation plan by changing the traditional idea from the long-term view is required that can reduce the damage in case of the next disaster. It is also necessary to reconsider the relationship between environmental conservation and rehabilitation projects. In the coastal region, significant environmental change has been already caused by the tsunami and land subsidence. Leaving a wide habitat in these rivers and coastal areas which will improve the ecological integrity can truly increase motivation and effectiveness of rehabilitation by improving fishery production and tourism value. Therefore, it is necessary to identify, in advance, high potential areas where biodiversity and ecological functions for material cycling will be increased, and reflect them for reconstruction master plan. In this paper, based on the above idea, issues to be discussed in the Ecology and Civil Engineering Society are presented for the reconstruction from the Tohoku earthquake and Tsunami.

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