3.2 Species compositions
Thirty-one species were collected, representing 11 families and 5
orders.
Twenty-nine species occurred in both impoundments and free-flowing
segments, of which the common species were Zacco platypus ,Acrossocheilus fasciatus , and Ctenogobius sp.(FO >40%), which were also abundance-dominant
(RA >10%) except for A. fasciatus . The
average species abundance per sample was 46.11 ± 29.43 (mean ± standard
deviation [SD]) individuals in impoundments and 62.28 ± 39.49 (mean
± standard deviation [SD]) individuals in free-flowing segments,
respectively. In addition, Ctenopharyngodon idella andMicropercops swinhonis (i.e., native-invasive species) were only
collected in impoundments, whereas Leptobotia guilinensis andParasinilabeo assimilis (i.e., native species) only occurred in
free-flowing segments (Table 1).
ANOSIM showed that fish assemblage composition strongly overlapped but
significantly differed between the impoundments and free-flowing
segments (Global R =0.04, P =0.014). The results of SIMPER
analyses showed the differences in assemblage composition resulted from
the abundance changes of 9 species between the two habitat types.
Compared with the free-flowing segments, the abundances of four native
(Z. platypus , Ctenogobius sp. , A. fasciatus , andVanmanenia stenosoma ) and one native-invasive (Rhodeus
ocellatus ) species decreased in the impoundments, whereas that of three
native-invasive (Misgurnus
anguillicaudatus , Odontobutis potamophila , and Carassius
auratus ) and one native (Cobitis rarus ) species increased (Table
2).