Biwa salmon (Oncorhynchus sp.), a species endemic to Lake Biwa in central Japan, has been stocked in Lake Biwa and its inlets for fisheries purposes since the Meiji period. In recent years, however, there has been a growing demand for ecosystem-based fishery resource management. I investigated spawning and swim-up habit of Biwa salmon in the Chinai River, an inlet of Lake Biwa, to provide fundamental knowledge on ecosystembased management for this species. Spawning redds of Biwa salmon were found from October to December, with the peak in November, suggesting that spawning period of Biwa salmon is longer and later than that of cherry (O. masou masou) and satsukimasu salmon (O. masou ishikawae) . Water depth and current velocity at spawning redds were 10-44 cm and 16-98 cm/s, respectively, with substrates dominated by pebbles (17-64 mm) . The number of egg pocket per redd was one or two, suggesting that Biwa salmon tended to create multiple small redds with a small number of eggs, rather than a single large redd containing a large number of eggs. Biwa salmon fry at the swim-up stage were caught from January to May. This swim-up period is also longer than the swim-up period of cherry salmon. Further, beginnings of the swim-up period (January) recorded by the present study (2011-12) were much earlier than those reported in this study river in the past (mid March in 1970-80's) . Considering increases in river water temperatures due to global warming, it would be better to protect the late spawning stock in December than the stock in October, because the latter is easily influenced by high water temperatures.

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Before the first infilling of Miharu Dam reservoir, a population of vulnerable species, Adonis ramosa, was found in 1996 on a shore slope that was supposed to be submerged by the initial impoundment. The main area of A. ramosa community was on a shore slope between the normal water level and surcharge water level of the reservoir. It was obvious that the initial impoundment would cause a devastating impact on the A. ramosa population. For the conservation purpose, we transplanted the most of A. ramosa individuals to another 4 places before the initial impoundment. In additon, for the examination purpose, we left a part of the community on the original habitat and monitored it. To examine the effect of transplant and influence of submersion, we monitored at 5 sites during 14 years since 1996, of which the first 2 years were taken as the pre-first filling and 12 years were done as the post-first filling. At all sites, A. ramosa individuals were observed after 12 years, though juveniles and blooming individuals were not observed at one transplant site. At the other 3 sites and the original habitat, juveniles and blooming individuals existed. It was suggested that re-production were continued at each site. Future prospect of the populations in the next 50 years were calculated using a Leslie matrix. It suggested that A. ramosa communities would be continued at site D and the original habitat, whereas they would be extinct at the other 3 sites. However, the conservation of A. ramosa population was succeeded since the total number of individuals and distribution in recent years were recovered and became larger than the previous time before the initial impoundment. The future populations will be sustainable for a long time at least 2 sites.

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Fish assemblage structure in spring-fed irrigation ponds in the Shigenobu River watershed (Ehime Prefecture) was compared between two periods, 1998-1999 and 2008, to examine effects of revetment construction and exotic largemouth bass (Micropterus salmoides). Two of the 11 study ponds were ‘altered ponds’, where bank revetment was constructed during the decade, whereas another pond was ‘bass pond’, where largemouth bss had established a self-reproducing population. Comparisons of species richness, density of each species and assemblage structure revealed that the most distinct change occurred in the bass pond, where most species other than largemouth bass showed drastic declines in population density. On the other hand, distinct fish-assemblage changes specific to the altered ponds were not found, despite considerable habitat changes due to the revetment construction work. Our data also revealed that two species, Tanakia lanceolata and Gnathopogon elongatus elongatus, which had been found from six and two ponds, respectively, disappeared in 2008. These disappearances may suggest an overall degradation of irrigationassociated aquatic systems (river-pond-ditch-paddy: alternative habitats for floodplainadapted fishes) as fish habitat.

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[in Japanese]

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We surveyed the distribution of oviposition sites and environmental characteristics around these sites of Tokyo salamander (Hynobius tokyoensis) at paddy fields of valley bottom in northeast region of Chiba Prefecture in 2012. Fifty oviposition sites were detected from mid-March to late-April. The number of egg sacs found in each oviposition site ranged from 1 to 52 (9.4 egg sacs on average), and small-scale oviposition sites, which had less than 10 egg sacs, shared over 70% of the total number of oviposition sites. Generalized linear model(GLM) analysis based on six variables related to landing of adults and larva after metamorphosis (canal width, water depth, sediment depth，distance to forest on slope, canal bank slope, and area of oviposition site), indicated that distance to forest on slope had a negative significant effect on their egg-sac number. Our results suggest the importance of spatial connectivity between oviposition sites and ordinary habitat for adults and larvae after metamorphosis( i.e. forest on slope) at micro spatial scale that allows the viability of Tokyo salamander population.

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