The variation of migration patterns in Dolly Varden Salvelinus malma in a stream with an artificial dam (erosion-control-dam) in the Shiretoko Peninsula, Hokkaido Island, Japan, at the southernmost part of its distribution, was examined by otolith Sr:Ca ratio analysis. All specimens from the abovedam area showed consistently low Sr:Ca ratios (<5.0 · 10 À3 ) throughout the otolith. In contrast, many specimens from the below-dam area had higher ratios (>5.0 · 10 À3 ) throughout the otolith or only at the outer part than do those from the above-dam area. This higher ratio is probably due to salinity effects. Specimen from the below-dam area could be divided into three types: (1) Consistently low Sr:Ca ratios throughout the otolith, being freshwater residents. (2) Low Sr:Ca ratios around the inner part of the otolith, and thereafter higher ratios toward the outer part, being typically anadromous. (3) Relatively higher Sr:Ca ratios throughout many or in some parts of the otolith, indicating that these have migrated from the freshwater to brackish water or seawater from the early life stage. These findings suggest that Dolly Varden has a high degree of plasticity in its migratory behavior.

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Nakagawa experimental forest of Hokkaido University is located in the middle Teshio River and some tributaries flow through the forest. The construction of Otoineppu bypass route started in 2007. This bypass route will pass through the forest. In order to evaluate the impacts of the road construction on stream ecosystem, a long-term monitoring of fish community and stream environmental characteristics have been conducted including before, during and after the road construction. The survey has been implemented on five streams in Teshio River (three streams inside the bypass construction zone and two streams outside the zone). Here, we report the data of species, body size and weight of fish sampled using an electrofishing unit and the data of stream environmental characteristics such as water temperature, water surface area, pH and EC. The three-pass removal method for fish sampling and measurement of stream environmental characteristics was conducted three times a year (mainly June, August and October) from 1999 to 2018. A total of 57,203 individuals were observed, belonging to 11 species in seven families. After bypass road construction started (2007), the number of fishes gradually increased at both bypass road construction and control sites. Occasionally, the number of fishes at the bypass construction site tended to be lower than at the control site, but there was not always noticeable difference between them.

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This study aimed to describe the change in the number of successful nests of the white-tailed eagle, Haliaeetus albicilla, for 25 years along the Teshio River (100 km), Japan, which is a new habitat for this endangered species and identify factors driving the number of nests. The number of nests grew from two to nine. The logistic function fitted in well with the growth, and the capacity of the study area sustaining the successful nests was estimated at 6.5. The precipitation in January and April explained the deviation of the observed values from the model prediction. In particular, heavy rain in April was associated with low numbers. Forty-six nest remains were collected from 17 nest locations. Twelve genera of birds, six genera of mammals, and four