Non-parametric methods – Tree and P-CFA – for the ecological evaluation and assessment of suitable aquatic habitats: A contribution to fish psychology

This study analyses multidimensional spawning habitat suitability of the fish species “Nase” (latin: Chondrostoma nasus). This is the first time non-parametric methods were used to better understand biotic habitat use in theory and practice. In particular, we tested (1) the Decision Tree technique, Chi-squared Automatic Interaction Detectors (CHAID), to identify specific habitat types and (2) Prediction-Configural Frequency Analysis (P-CFA) to test for statistical significance. The combination of both non-parametric methods, CHAID and P-CFA, enabled the identification, prediction and interpretation of most typical significant spawning habitats, and we were also able to determine non-typical habitat types, e.g., types in contrast to antitypes. The gradual combination of these two methods underlined three significant habitat types: shaded habitat, fine and coarse substrate habitat depending on high flow velocity. The study affirmed the importance for fish species of shading and riparian vegetation along river banks. In addition, this method provides a weighting of interactions between specific habitat characteristics. The results demonstrate that efficient river restoration requires re-establishing riparian vegetation as well as the open river continuum and hydro-morphological improvements to habitats.