Importance of the Temporal Aspects of Habitat Hydraulics to Fish Population Studies

Abstract

The direct and indirect influences of hydrology and hydraulics on the usability of stream habitats by stream fish are discussed. Most habitat–hydraulic models in use today emphasize the spatial aspects of habitat quality and quantity. It is our contention that the temporal dynamics of habitat quantity are a major influence, determining fish population responses in riverine environments. This may manifest through dramatic shifts in the velocity and temperature distributions over seasons and years as influenced by climatic conditions as well as reservoir operations. Time series simulations of usable habitat available to various life stages of brown and rainbow trout and smallmouth bass populations demonstrate that the usable space and its stability during the early life history is directly translated into year‐class‐strength for these fish populations. Riverine ecosystems are temporally dynamic due to the stochastic nature of precipitation events. Therefore an understanding of the temporal aspects of streamflow and habitat is essential to designing water management schemes intended to protect, enhance or restore riverine fish populations.

The geomorphic and ecological effectiveness of habitat rehabilitation works: Continuous measurement of scour and fill around large logs in sand-bed streams

“…Several structures exhibited cycles of deposition: deep scour holes… would alternate with sandbars" (p.499). This reflects the conclusion of Stalnaker et al (1996) who warned that "the temporal dynamics of habitat quantity are a major influence determining fish population responses in riverine environments".…”

Discharge and hydraulic interactions in contrasting channel morphologies and their influence on site utilization by spawning Atlantic salmon (Salmo salar)

“…The rate of change may be a crucial hydrological variable that habitat models, to date, have largely failed to consider when assessing or making recommendations for environmental flows. Although time series analysis is typically used in PHABSIM-type studies to examine the influence of flow variation on the temporal distribution of habitat (Stalnaker et al 1994;Dunbar et al 1996), this does not explicitly account for the rate of change of flow. Work in other rivers, particularly larger and less hydrologically dynamic ones, is needed to determine the broader significance of the rate of change of discharge for spawning Atlantic salmon.…”

Dams and geomorphology: Research progress and future directions

“…Thus, Petts et al (1993) related macroinvertebrate response to flow regulation on the River Rede, UK to (i) sector-scale changes of channel form and (ii) local-scale hydraulic variations associated with different bedforms (clean gravel riffles, sandy gravel bars, shallow gravel runs, and cobble steps) superimposed upon water quality and trophic gradients downstream of the dam. Subsequently, the temporal variability of streamflow and habitat became the focus of attention, especially below hydro-peaking dams (Gore et al, 1994;Stalnaker et al, 1996;Valentin et al, 1996) and in relation to flushing flows to remove fine sediment accumulations from fish spawning habitat (Milhous, 1998).…”