Author(s): Shinji Urabe; Yasuhiro Takemon; Tetsuya Sumi
Linked Author(s): Tetsuya Sumi
Keywords: Yu-fish; Climate change; Distributed hydrological model; Water temperature
Abstract: Juvenile Ayu-fish (Plecoglossus altivelis) migrate from the coast to rivers every spring showing a wide range of yearly variationsin abundance. For inland fisheries in Japan, a considerable number of cultivated Ayu-fish are released in spring in order to compensate the shortage of upstream migration and to increase annual production of the fish. Therefore, it is beneficial if we could predict the abundance of upstream migration before the season. In this paper, we investigated the environmental factors influencing thenumberofAyu-fishmigratingupstreaminthe Yodo River-Osaka Bay basin systemand established a multiple regression formulausing chlorophyll-a in Oct (X 1) and sea water temperature in winter (X 2). Y=89340X 1 -288402X 2 +2579513. In addition, impacts of climate change on the number of Ayu-fish migrating upstream in the Yodo River was also assessed under CMIP3 climate models by developing distributed hydrological model to estimate river discharge and water temperature in future (2097~2110). Under the A1B scenario, futuremean water temperature at the river mouth from January to March increased by about 2 degrees and the future number of upstream migration was estimated to decrease. As a mitigation measure of increasing water temperature by climate change, lowering temperature of the sewage treatment waterdrained into river was found to be effective based on comparison betweenheat flux from the sewage treatment water into the river and increasing amount of heat flux in the river by climate change.