Geomorphic river classifications based on different methods coincide in predicting fish assemblage structure

Keywords: Fluvial geomorphology, invasive species, indigenous territory, hydrogeomorphic processes
Abstract Type: Poster Abstract

Abstract

River classification is a crucial first step in comprehending river ecosystems and formulating management guidelines. We applied two geomorphic categorization methodologies at the segment scale, the Geomorphic Units Survey Classification System (GUS) and the Functional Process Zones (FPZ), to analyze an Andean river. Both classifications are relevant for the ecological aspects of rivers, such as the type of material in the riverbed and the speed of the water that creates habitat for various plants and animals. We sought to evaluate the association between fish assemblage structure and river type determined by each approach (GUS and FPZ). Fish sampling was done in conjunction with local indigenous Mapuche-Pehuenche community members. Non-parametrical multivariate statistical analyses were conducted to quantify and describe geomorphological patterns and whether fish assemblages responded consistently with river classifications. GUS and FPZ results identified similar river types, which were associated with distinct fish assemblage structure. Geomorphological factors that best characterized the distribution pattern were elevation, confinement, and valley floor width. Confined rivers accommodated fish assemblages dominated by invasive trout (Salmo trutta and Oncorhynchus mykiss). Unconfined rivers located at higher elevation had greater temporal variability and were composed of trout and native Trichomycterus areolatus. Semiconfined rivers presented the highest geomorphic variability and were associated with high spatial and temporal variability of fish assemblages with both native and non-native species. The association between fish assemblages and fluvial geomorphology can be used to prioritize invasive fish species control and improve management and restoring techniques in Andean rivers with a variety of human activities.