Biological and environmental characteristics significantly impact the swimming performance: A 5‐year study on 76 fish species from 7 rivers in Southwest China

Fish swimming performance is crucial for population survival. This study investigated factors influencing the swimming performance of endemic fish in Southwest China, sampling 2077 wild fish (76 species) from seven rivers between 2019 and 2024. Induced swimming speed ( U ind ) was primarily affected by fish morphology, followed by species identity and spatial factors. For critical ( U crit ) and burst ( U burst ) speeds, species identity was the main driver, followed by morphology and water quality. Fish from mountainous rivers exhibited stronger U crit and U burst but weaker U ind , while those from high‐altitude, cold‐water rivers showed the opposite trend. Higher water temperature, flow, slope and dissolved oxygen positively correlated with U crit and U burst . Elevated COD Mn , NH 3 ‐N, total phosphorus and total nitrogen were negatively correlated with U ind and U crit but positively correlated with U burst . Elongated‐shaped Hemibagrus macropterus demonstrated superior overall swimming performance. Tail‐beat frequency remained stable at low U crit , increased at medium U crit and then stabilized or dropped at high U crit . These findings are vital for conserving rare and endemic fish in Southwest China.