河川型オショロコマの流程分布に対する水温の影響および地球温暖化による生息空間の縮小予測

概要

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To estimate potential loss of thermal habitat for Dolly Varden (Salvelinus malma) due to global warming, the relationship of population density and growth of Dolly Varden to stream temperatures was studied during summer in a cold spring-fed stream at southern margin of their range in southern Hokkaido, Japan. A simple regression equation was obtained for the longitudinal gradient of the stream temperature, logarithmically increasing downstream. Summer habitat of Dolly Varden was delimited by a thermal barrier of about 16℃, located approximately 10km downstream from the headspring, with fish density decreasing downstream. During mid summer, the specific growth rate of Dolly Varden decreased near the thermal barrier (probably due to too-high stream temperature), but not in the upper reaches of the stream where the temperature was lower. The upstream movement of the thermal barrier as a result of global warming was estimated from the elevation of groundwater temperatures and regression analysis of the longitudinal gradient of the stream temperature. For increases of 1.0-4.0℃ mean annual air temperature, the summer thermal habitat for Dolly Varden would be reduced by 25.0-74.0%.
野生生物保護学会の論文