Comparison of different spatial fish communities
Noticeable differences were observed in the fish species composition between the upper and lower reaches of the Chishui River Basin, as shown in Figure 2(b). However, no significant differences were observed between upstream and downstream reach. Nonetheless, there were significant differences between the upstream and downstream tributaries, indicating that disparities between the upstream and downstream tributaries could be attributed to the fish communities in the tributaries. Studies have revealed that fish diversity is associated with river area (Oberdorff et al., 2019) and habitat heterogeneity (Hugueny et al., 2010). Therefore, habitat heterogeneity may be a more influential factor for community differences. Furthermore, in the comparison of transverse gradients, it was discovered that the DaTong River exhibited the highest level of α diversity among all tributaries. This finding differs from the results of traditional survey studies conducted at the same position on the Xishui River (Liu et al. 2020). We believe that the topography and hydrological conditions of the DaTong River tend to impede traditional surveys, leading to an underestimation of tributary diversity. Conversely, the gentle flow speed and easy accessibility of the Xishui River facilitated a tributary survey which was more comprehensive. Therefore, the status of the DaTong River should be elevated to the same level as that of the Xishui River.