Fish diversity responds to environmental variables and
anthropogenic activities
The CCA results showed that the explanatory variance was 4.06% (P =
0.001) for the first axis and 3.1% (P = 0.004) for the second axis.
These results indicate that the first axis significantly separated the
environmental variables from different groups based on fish communities
(Fig. 7). The ranking results revealed that altitude, river width,
dissolved oxygen, flow rate, and pH had substantial effects on community
composition.
Finally, we conducted a Pearson analysis of the environmental variables
and species richness index. The results showed a significant positive
correlation between water temperature (TE) and fish richness (P = 0.027;
Fig. 8). However, there was a significant negative correlation between
altitude (ASL), electrical conductivity (EC), and fish species richness
(P = 0.0018 and P = 0.0081, respectively).
Analysis of the data using a generalized additive model revealed that
the impact of FPT and land use on fish species richness was negligible.
However, it is important to mention that the percentage of impervious
area, which is commonly used as an indicator of urbanization, had some
effect on fish species richness. Specifically, fish species richness was
higher at lower percentages of impervious area, but the increase was not
statistically significant (Fig. 9).