3.1 Spatial distribution pattern of fish communities along the
river
There were 131 fish species belonging to 22 orders, 59 families, and 103
genera detected by the eDNA sampling protocol. There were 92 fish
species belonging to 16 orders, 48 families, and 79 genera detected by
electrofishing in situ. The fish
species detected by eDNA across the 38 sampling sites contained all the
fish species sampled by electrofishing, indicating that the capacity of
eDNA to find species was stronger than that of electrofishing. NMDS
results showed that, regardless of the data types (i.e., novel eDNA OTU
richness and traditional
biological counting), the
relative percentage (%) of OTU
richness (Fig. 2A), individual number (Fig. 2B), and biomass (Fig. 2C)
could group the 38 sampling sites into eight spatial zones, including I
(L1 − L2 and Z1 – Z3), II (L3 − L6), III (L7 − L11 and Z4), IV (L12 −
L14 and P1 − P2), V (Z6 – Z7 and P3 − P4), VI (Z8 − Z11), VII (P5 −
P8), and VIII (Z5 and P9 − P12). Along the river continuum, these zones
were distributed in sections with heterogeneous habitats, including
headwaters, upper stream, middle river, lower reaches, and river mouth.
Our results suggested that eDNA
could indicate the spatial
distribution pattern of fish communities as well as the pattern
reflected by electrofishing.