# Swimming Performance and Behavior of High-Altitude Fish in High-Flow Velocity Environments

## TL;DR

This study examines how high-altitude fish swim and make decisions in fast-moving water, revealing they are more capable than previously thought and providing insights for better fishway design.

## Contribution

The study introduces a systematic method to quantify the extreme swimming abilities and nonlinear behavioral responses of high-altitude fish in high-flow environments.

## Key findings

- S. oconnori can swim much faster than previously estimated and adapts its path based on movement mode and endurance.
- The fish shows high sensitivity to changes in exercise intensity and prioritizes energy conservation and stability in fast currents.
- The study provides scientific guidance for optimizing fishway design and hydraulic thresholds for high-altitude species.

## Abstract

Fishways are crucial structures that help fish navigate obstacles like dams. Their design largely depends on our understanding of fish swimming performance and behavior. Traditional methods often underestimate fish capabilities, especially neglecting the performance and behavior of high-altitude species in fast-flowing waters. This study focuses on a high-altitude fish species called Schizothorax oconnori Lloyd, 1908 (S. oconnori) from the Tibetan Plateau. Using flume experiments and behavioral models, the study accurately quantifies the fish’s swimming performance and complex decision-making behaviors in fast currents. The results show that these fish can swim much faster than previously thought, and they cleverly choose their swimming paths based on their movement mode and endurance state to conserve energy and maintain stability. This research provides scientific guidance for setting hydraulic thresholds and developing protection strategies for fishways.

The optimization of fishway design relies on a deep understanding of fish swimming performance and behavioral traits. Traditional methods often underestimate fish swimming performance and overlook their behavior under high-flow conditions, particularly in the context of high-altitude species. This study, based on an open-channel flume system and combined with high-speed video tracking and Acoustic Doppler Velocity (ADV) measurements, constructs a Resource Selection Function-Generalized Additive Mixed Models (RSF-GAMMs) to quantify the swimming performance and behavior mechanisms of the high-altitude species, Schizothorax oconnori Lloyd, 1908 (S. oconnori), in high-velocity environments. The results show that S. oconnori significantly outperforms traditional swimming tests and exhibits strong dependence on movement modes. Endurance analysis reveals the breakpoints of endurance models, indicating the species’ high sensitivity to variations in exercise intensity, showcasing the unique physiological and behavioral characteristics of high-altitude fish. In high-velocity conditions, adult S. oconnori primarily aims to optimize energy conservation and stability, selectively choosing water bodies with varying disturbance levels depending on its movement mode and endurance state, thus optimizing path selection. This study presents a systematic method for quantifying the extreme swimming abilities and nonlinear behavioral responses of adult S. oconnori under complex flow conditions, providing scientific guidance for setting hydraulic thresholds and developing protection strategies for fishways.