Spatio-temporal changes in habitat potential of endangered freshwater fish in Japan

In recent years, biodiversity conservation and ecosystem restoration have been key issues of watershed management in many countries. To maintain or restore the environmental quality of watersheds, we need to assess the impact of anthropogenic changes on stream ecosystems with accuracy. In addition, watershed conservation planners have to make strategic plans and determine priorities of each conservation activity.

A new monitoring methodology to evaluate the change of habitat condition for freshwater fish based on a predictive habitat model using logistic regression was developed and applied to the whole of Japan. The main contributions of our approach were 1) the construction of a Geographical Information System (GIS) database that integrates many types of data, including freshwater fish species, water quality, habitat fragmentation by damming, geology, and climate; 2) spatial analysis for quantitative assessment and predictive habitat modeling using logistic regression to combine fish survey data and environmental habitat factors to determine critical and major habitat variables for each target fish; and 3) digital mapping and changes detection of fish habitat potential for targeted endangered fish species to show habitat distribution and spatio-temporal changes of habitat potential over a 25-year period (from 1977 to 2002). We found that predicted suitable habitat and actual fish habitat showed high overlap, and that habitat conditions and distribution patterns of target freshwater fish had been affected by major habitat variables to target species respectively.