Abstract:
Research on intermittent streams has linked deep pools with successful
completion of critical life history requirements; however, few studies have investigated
this concept in larger rivers. I compared fish assemblages, including species richness and
fish density, in riffles, wadeable pools, and non-wadeable pools of the Neosho River, a 5th- order perennial warmwater river in Kansas, USA. Samples were collected by trawl
during spawning and post-spawning seasons at eight sites from May to November 2018. I
predicted that these mesohabitats would support disparate fish assemblages that changed
in structure seasonally. I found that spatial patterns of fish assemblage structure were
largely explained by differences between riffle and pool samples, consistent with that
prediction. Species composition also varied between wadeable and non-wadeable pools,
with Ghost Shiner (Notropis buchanani) abundance greatest in non-wadeable pools and
Shortnose Gar (Lepisosteus platostomus), Smallmouth Buffalo (Ictiobus bubalus), and
White Crappie (Pomoxis annularis) collected only in this mesohabitat. Temporal patterns
reflected higher species richness and fish density during spawn than post-spawn, with the
density of fishes greatest in riffles and wadeable pools during the spawn but greatest in
wadeable pools during post-spawn. Results were dependent on whether area- or volume
based densities were analyzed, as more significant non-wadeable pool comparisons,
higher riffle densities, and more indicator species were identified using volume-based
densities. When sampling a diverse fish assemblage with species associated with surface,
benthic, and water column habitats, both metrics and deep pools should be examined.
