Title : A trait for a trait: Imputing critical swimming speed (U-crit) of data deficient freshwater fish
Abstract:
Covering less than 1% of Earth's surface, freshwater bodies are critical yet endangered ecosystems. Freshwater species populations in rivers have experienced an alarming 83% decline since 1970, primarily due to threats like urbanization, pollution, deforestation, and dam construction. These factors disrupt freshwater networks, leading to altered river discharge and establishing the freshwater fish as the most endangered biota in the Anthropocene. Despite the urgent need for conservation strategies, their development is hindered by a lack of data on essential physiological traits of riverine fish, such as critical swimming speed. This research addresses this gap by quantifying these traits for individual freshwater fish species worldwide. We reveal, for the first time, the critical swimming speed (U-crit) of all freshwater fish species and the key morphological factors influencing it. Through literature review, we gathered information regarding 211 species’ U-crit, which allowed us to identify the main trait-trait relationships. Body length, caudal peduncle throttling, body elongation, and pectoral fin shape were found to be of high importance and strongly related with U-crit. Using these traits and phylogenetic information, we employed a random forest model to successfully impute the U-crit of 14,000 fish species. This novel approach integrates ecological traits, phylogeny, and environmental variables to enhance understanding of riverine fish physiological processes. By characterizing the swimming performance of the global freshwater fish population accurately, this study aims to provide a robust foundation for both research studies and policy-makers, informing effective conservation strategies in the face of global threats.
