Estimating and classifying spatial and temporal distributions of flow conditions for fish habitats by using geostatistical approaches with measured flow and fish data

Abstract

This study investigated the relationship between the distribution of Sicyopterus japonicus, current velocity and water depth in four reaches along Datuan Stream in northern Taiwan during winter of 2007 and spring of 2008. The spatial distributions of current velocity and water depth were estimated by kriging from the stream mouth to the upstream section. The empirical rule method and the Froude number method with kriging estimated distributions of the current velocity and water depth were incorporated into a geographical information system (GIS) and used to classify flow conditions at the investigated reaches. Indicator kriging was used to estimate the probability of the presence of S. japonicus and superimposed on the estimated flow conditions at each reach. The field results showed that, in each investigated season, the average current velocity was low in the downstream and upstream reaches, but high in the middle stream reach. The flow conditions based on kriging estimated distribution of water velocity and water depth at the investigated reaches accurately reflect flow conditions at each reach along the stream. Geostatistical approaches, such as kriging and indicator kriging, can be used to estimate the flows and the appearance probability of fish accurately. Moreover, the overlapping maps of the flow conditions and the probabilities indicate that the preferences ofS. japonicus vary in different reaches and seasons. Based on the migration behavior of S. japonicus, the classification of the empirical rule flow classification method with geostatistical approaches in GIS can be used to estimate the preferences of S. japonicus in Datuan stream effectively. © 2010 Springer-Verlag Berlin Heidelberg.