Fish use of stage-specific fluvial habitats as refuge patches during a flood in a low-gradient Illinois stream

Abstract

A stage-specific habitat classification scheme was developed emphasizing the ecological importance of habitat space as flow refugia for fish. Habitat units were based on planform and channel morphology and the resulting three-dimensional hydraulic patterns that form during floods. Fish were sampled in specific habitat patches using prepositioned areal electrofishing devices at two high-flow stages, near bankfull flow and one-half bankfull flow, during a flood. Fish were also sampled at baseflow immediately following the flood to compare changes in habitat use related to flow stage. During the bankfull stage, fish were found to use floodplain habitat units identified as vegetated point bars and concave-bank benches. During the one-half bank-full stage, fish density and biomass were greater in low-velocity habitat units identified as deflection eddies and expansion eddies than in the high-velocity habitat unit identified as the channel thalweg. Once flow returned to baseflow, fish density and biomass were greater in the main channel habitat units (pools, riffles, and glides) than in lateral habitat units identified as submerged point bars and lateral backwaters. This study provided a framework to quantify flow refugia in low-gradient streams, which is especially important in the restoration of anthropogenically disturbed watersheds that have lost habitat connectivity.

Movement and Mortality of Adult Brown Trout in the Motupiko River, New Zealand: Effects of Water Temperature, Flow, and Flooding

“…Trout also seek refuge from adverse environmental conditions in winter (Cunjak 1996) and summer (Nielsen et al 1994;Ebersole et al 2003). Floods may also initiate longitudinal or lateral movement in fish, either to take advantage of easier passage during high flow conditions (Dedual and Jowett 1999;Natsumeda 2003) or in an effort to avoid the impact of floods (Jowett and Richardson 1994;Schwartz and Herricks 2005). Juvenile trout abundance tends to decline after severe floods (Jowett and Richardson 1989;Hayes 1995;Harvey et al 1999;Nislow et al 2002).…”

Use of Ecohydraulic-Based Mesohabitat Classification and Fish Species Traits for Stream Restoration Design

“…During flood flows, stage height determines what high-flow mesohabitat units are available for fish occupancy. Velocities in the high-velocity corridor ranged from 0.56 to 1.49 m·s −1 , and they were mostly zero in the low-velocity areas though velocities between 0.03 and 0.08 m·s −1 were measured at some units [253].…”

“…Though these classification schemes begin to integrate physical habitat space with ecological functions at low flow stages, 3D mesoscale hydraulics patterns are not applied to habitat delineation at both low-and high-flow stages. At higher flow stages, channel hydraulics for the same habitat space change, as well as the fish use and survival strategies [120,[250][251][252][253]. For example, Wadson and Rowntree (1998) [251] applied the biotope classification system to three different flow stages and reported percentages of pool and riffle units decreased with higher flow stages, while percent glide units increased.…”

“…These areas develop as flows interact with the channel morphology including planform sinuosity, floodplain-channel morphology, bed topography and large roughness elements influencing the 3D hydraulic characteristics [71,128,135,137,253,262,[270][271][272][273].…”

“…elements influencing the 3D hydraulic characteristics [71,128,135,137,253,262,[270][271][272][273]. Three hydraulic categories were used to classify high-flow mesohabitat units; they include: (1) the high-velocity corridor within the active channel, (2) low-velocity areas along the active channel margins and (3) low-velocity areas at the channel-floodplain interface [253].…”