Water flow and substrate preferences of Schizothorax wangchiachii (Fang, 1936)

Abstract

Understanding the habitat preferences of a fish species is crucial for protecting fish resources because it can guide development of appropriate conservation measures. Field surveys suggest that water flow velocity and substrate are the main influences on fish microhabitat selection. Controlled experiments are better suited to assessing fish microhabitat preferences than field surveys but experimental data are not yet sufficient for cyprinids. We conducted experiments with Schizothorax wangchiachii in an experimental system comprised of four parallel channels, with a different substrate type in each channel. Fish preference for each substrate was tested at four levels of water flow. Results show that flow velocity influences channel preference more than substrate type. Test fish entered channels more frequently as flow velocity increased from 0.01 m/s to 0.37 m/s. Surface stability and interstitial space were the major factors influencing preference for substrate type. The horizontal velocity gradient perpendicular to flow direction, resulting in shear stress, was hypothesized to be a third explanatory variable for channel preference, but it did not significantly influence channel preference. Test fish spent most of the day in a shaded (shelter) area and were far less active during the day than at night. This study provides information on S. wangchiachii preferences for water flow and substrate, circadian rhythm and daylight sheltering, information that will help guide efforts to conserve wild populations of S. wangchiachii.