Fish diversity responds to environmental variables and
anthropogenic activities
In this study, we found that changes in distribution and diversity in
the Chishui River Basin were predominantly influenced by environmental
factors. The results of our CCA showed that altitude had a significant
impact on upstream fish richness, resulting in a significant decrease in
fish species richness with increasing altitude. Similarly, conductivity
significantly affected downstream fish richness (Chen et al., 2020). Our
findings demonstrated a significant decrease in fish species richness
with increasing conductivity. Previous studies have highlighted the
importance of these two factors in affecting fish species richness. The
altitude difference between the upper and lower reaches of the Chishui
River can reach 1180 m, leading to changes in water temperature and flow
rate. These changes resulted in noticeable differences in upstream,
middle, and downstream fish habitats, leading to variations in fish
species composition. For instance, Sinocrosssocheilus labiatusand other fish adapted to cold-water environments were only found in the
upstream basin in this study, leading to specific fish species upstream
that exhibited significant differences from those downstream.
Human activity in the downstream basin is more intensive than in the
upstream reaches, resulting in increased water pollution and impurities.
As a result, most fish are intolerant of this environment (Bertora et
al., 2022), leading to a decrease in fish species. However, tolerant
fish species, such as Zacco platypus , have shown an increase in
population numbers (Yeom et al. 2007; Morosawa 2011). In summary, our
research showed that environmental factors such as altitude and
conductivity play a significant role in the distribution and diversity
of fish species in the Chishui River Basin.
This study found that the impact of anthropogenic activities,
specifically the use of fertilizers, pesticides, and land, on the study
area was not significant. Based on our analysis, we believe that this
result can only be considered valid under the assumption that the
intensity of anthropogenic activity in the Chishui River Basin has not
yet reached the threshold affecting fish diversity. Additionally, human
influencing factors, such as fishing intensity, disappeared after the
implementation of the fishing ban. This policy has led to fish in the
Chishui River Basin being primarily affected by environmental factors,
which is similar to the natural succession stage and conducive to the
community reconstruction process (Liu et al. 2021). In summary, the
results of this study suggest that the current environmental conditions
in the Chishui River Basin are favorable for community reconstruction.