# Study on the Selective Behavior of Brachymystax tsinlingensis Li, 1966 (Order: Saloniformes, Family: Salmonidae) on Substrate Color and Type

## TL;DR

This study examines how Brachymystax tsinlingensis fish choose different substrate colors and types, which helps in understanding their habitat preferences for better conservation and breeding.

## Contribution

The study identifies specific substrate preferences of Brachymystax tsinlingensis at different life stages, offering practical guidance for their cultivation and habitat restoration.

## Key findings

- B. tsinlingensis prefers black substrate and avoids blue in both light and dark environments.
- Pre-smolts and post-smolts prefer sandy substrate, while juveniles prefer medium gravel.
- Substrate preferences aid in hiding from predators and improving survival rates.

## Abstract

Brachymystax tsinlingensis is a unique cold-water fish locally distributed in China. As early as 1988, it has been included in the national second-class protection of wildlife; its protection is crucial, but because of its sensitive habitat and unique habits—especially on the choice of substrate environment is extremely harsh—the substrate environment was determined to play an important role in the protection of B. tsinlingensis. For this reason, this study used the flume experiment method to observe the substrate selection behavior of B. tsinlingensis, aiming to clarify the characteristics of substrate selection behavior of B. tsinlingensis, grasp its habitat preferences, and provide technical guidance for environmental selection in its seedling cultivation and resource restoration process.

Substrate is an important component of a fish’s habitat environment. Fish preferences for substrate influence their growth and development, feeding, hiding, schooling, and reproduction. To explore the habitat preference of Brachymystax tsinlingensis, this study was conducted on the preferences of B. pre-smolts, post-smolts, and juveniles for three substrate colors, white, blue, and black, and four substrate types, sand (<0.5 cm in diameter), small gravel (1–2 cm in diameter), medium gravel (5–7 cm in diameter), and large gravel (12–16 cm in diameter), which were investigated in light (10–60 lx) and dark (no light) environments. The results showed that the individual populations of B. tsinlingensis in three periods of time had a clear preference for substrate color, preferring black substrate and staying away from blue substrate under both light and dark environmental conditions; B. tsinlingensis pre-smolts and post-smolts preferred sandy substrate, and juveniles preferred medium gravel substrate. The choice of substrate color and substrate type by B. tsinlingensis is a manifestation of the living environment characteristics of this species, which is conducive to their hiding, better avoidance of enemies, and improvement of their survival rate. Based on the research results and the early biological characteristics of B. tsinlingensis, it is recommended to use black or dark substrate during the cultivation of B. tsinlingensis fry. During the larval fish stage, a sandy substrate environment should be provided. During the juvenile fish stage, a medium-gravel environment should be provided.