2.2 Field survey
A total of 106 sites (53
impoundments and 53 free-flowing segments) were sampled across the
Wannan Mountains only in the wet
season (August 2015). Meanwhile, the
highland streams discharges of this
region are characterized by flashy
pulses with high-flow conditions during the wet season (Yan et al.,
2013). Following the standardized methods (i.e., stream length and
sampling time) of Li et al. (2021), stream fish assemblages were sampled
at each site using a backpack electrofishing unit (CWB-2000 P, China;
12V import and 250V export) by wading in two passes. Based on Nelson’s
(2006) classification method, all fishes were identified in the field to
species and counted. At least 20 adult specimens of each species were
used to measure the traits, and all adult specimens were measured when
the species contained less than 20 adult individuals. Whenever possible,
only a fraction of abundance-dominant species returned to the sampling
sites if alive and the remaining species were retained for further
laboratory identification and measurement.
Fish handling procedures were
performed following bioethical protocols established by the Anhui Normal
University Animal Ethic Committee.
We characterized the local habitat conditions of each sampling site
using seven habitat variables, including wetted width (m), water depth
(m), current velocity (m/s), dissolved oxygen (mg/L), water temperature
(°C), substrate coarseness, and heterogeneity. The wetted width was
measured along three equally spaced transects that ran across the
surveyed stream channel. The water depth was measured at three equally
spaced points along each transect. The current velocity was quantified
at 60% of the water depth at each point using FP111 (USA). Dissolved
oxygen and water temperatures were measured using an YSI Professional
Plus meter (USA). The substrate was quantified within each sample site
and divided into 10 cross sections based on the size-class frequency
method of Bain et al. (1985): particle size 0 = 0–0.059 mm, 1 = 0.06–1
mm, 2 = 2–15 mm, 3 = 16–63 mm, 4 = 64–256 mm, and 5 =
>256 mm. The mean and standard deviation of the substrate
values were used as indices of substrate coarseness and heterogeneity,
respectively.