3.3 The diversity relationships between eDNA and electrofishing
sampling
The linear regression results showed that the relationships between the
alpha diversity calculated by eDNA OTU richness and fish individual
number exhibited significant (P < 0.05) positive
correlations (Fig. 4A). The regression equation is fitted as Y =
0.9572∙X + 0.5425 (R ² = 0.8218), where Y is the
number-based diversity, X is the eDNA-based diversity, andR -squared (R 2) measures how close the
data points are to the fitted line. The linear regression between the
fish diversity calculated by eDNA OTU richness and by fish biomass
(i.e., wet weight) exhibited significant (P < 0.05)
positive correlations. The regression equation is fitted as Y =
0.4339∙X + 2.3043 (R ² = 0.4558), where Y is the
biomass-based diversity and X is the eDNA-based diversity (Fig.
4B). These results indicated that the eDNA metabarcoding protocol could
reflect the alpha diversity of local fish communities as well as the
diversity determined by traditional biological counting, and the
eDNA-based diversity had a higher matching degree with number-based
diversity than with biomass-based diversity. In addition,R 2 showed significant (P <
0.05) intergroup differences between the spatial zones (Fig. 4C). The
highest R 2 values were observed in zones I − II
and VII – VIII, which were significantly higher than those in zones IV
− V. This result indicated that the eDNA-based diversity had higher
linear regression with number-based diversity in headwater and the
estuarial zones.