4.4 Use of fish diversity to evaluate the water quality
Considering different monitoring targets, the use of eDNA-based fish
monitoring could be summarized into three goals: 1) water pollution that
may reduce fish diversity in water bodies, 2) evaluation of the effects
of serious environmental events on local aquatic communities, and 3)
tracing the target species such as indicator, protected, and endangered
fish in the river system. Our results demonstrated that the
environmental influence on fish distribution and composition analysed by
the eDNA method showed a similar tendency to that analysed by the
traditional method (e.g., individual number and biomass), suggesting
that eDNA is a useful tool for monitoring biological communities in the
field. In this study, DO, velocity, salinity, depth,
CODMn (or BOD5), and the bacteria amount
in the water were the key environmental factors that influenced the fish
communities. In fact, given that fishes are not only the crucial
components of the local food web, but also the high-level predators that
exhibit top-down control effects, key environmental factors that
influence fish distribution and composition may also influence food web
properties (e.g., ominivory, connectivity and stability; see Wang et
al., 2018a; Wang et al., 2019b; Wang et al., 2021a). Our further
research will focus on the eDNA-based relationships between the
attributes of fish communities and those of invertebrate communities as
well as on the structure and functioning of aquatic food webs.