# Effects of Biological Characteristics and Environmental Factors on Swimming Performance of Endemic Fish in Southwest China

## TL;DR

This study examines how biological traits and environmental factors affect the swimming performance of endemic fish in Southwest China, highlighting the importance of species, weight, and habitat preferences.

## Contribution

The study identifies weight parameters and species-specific traits as stronger predictors of swimming performance than body length in endemic fish.

## Key findings

- Weight parameters correlated more strongly with swimming ability than body length parameters.
- Fish in lotic environments and with streamlined morphology showed distinct swimming performance patterns.
- Swimming performance varied between spawning and non-spawning periods across species.

## Abstract

Fish swimming is crucial to their survival and reproduction, and is usually influenced by species, morphology, habitat environment and physiological condition. Understanding the changes in fish swimming ability and identifying the driving factors behind these changes are of pressing importance. Our findings showed that body length parameters had a minimal effect on the induced swimming speed, but played a positive role in critical and burst swimming ability. Weight parameters were more highly correlated with swimming ability than body length parameters. Fish preferring the lotic environment exhibited higher Ucrit and Uburst, and fish with a streamlined morphology had smaller Uind. The burst swimming speed of fish during the spawning period was slower than that during the non-spawning period. Generally, the swimming ability was mainly influenced by the species identity, followed by environmental conditions and morphological factors. The findings of this study are of great significance to the conservation of rare and endemic fish in mountainous rivers, and could provide a theoretical basis and data support for the design of river restoration measures.

Swimming is crucial to fish survival and reproduction, and is usually influenced by species, morphology, habitat environment and physiological condition. Understanding the changes in fish swimming ability and identifying the driving factors behind these changes is vital. In this study, seven endemic fish species from the Qingshui River, an important tributary of the upper Pearl River in Southwest China, were used to explore the effects of biological and environmental factors on fish swimming ability. The results indicated that the body length parameters had a minimal effect on the induced swimming speed (Uind) but played a positive role in critical and burst swimming ability (Ucrit and Uburst). Weight (W) and W/SL (the ratio of weight to standard body length) correlated more highly with swimming ability than body length parameters. Fish preferring the lotic environment exhibited higher Ucrit and Uburst, and fish with a streamlined morphology had a smaller Uind. The Uind, Uind/SL, Uind/W and Uind/(W/SL) of Discogobio yunnanensis (Regan, 1907) and Pseudocrossocheilus tridentis (Cui & Chu, 1986) were significantly higher during the spawning period. Acrossocheilus yunnanensis (Regan, 1904) performed better during the spawning period in Ucrit and Ucrit/SL. The Uburst of fish during the spawning period was smaller than that during the non-spawning period. Generally, the species difference had the greatest contribution to the swimming ability difference, followed by environmental conditions and fish morphology.