A seismic monitoring approach to detect and quantify river sediment mobilization by steelhead redd‐building activity

Abstract

The role of spawning salmonids in altering river bed morphology and sediment transport is significant, yet poorly understood. This is due, in large part, to limitations in monitoring the redd‐building process in a continuous and spatially extended way. A complementary approach may be provided through the use of a small seismic sensor network analysing the ground motion signals generated by the agitation of sediment during the redd‐building process. We successfully tested the viability of this approach by detecting and locating artificially generated redd signals in a reach of the Mashel River, Washington State, USA. We then utilize records of 17 seismic stations, in which we automatically detected seismic events that were subsequently manually checked, yielding a catalogue of 45 potential redd‐building events. Such redd‐building events typically lasted between 1 and 20 min and consisted of a series of clusters of 50–100 short energetic pulses in the 20–60 Hz frequency range. The majority (>90%) of these redd‐building events occurred within 11 days, predominantly during the early morning and late afternoon. The seismically derived locations of the signals were in agreement with independently mapped redds. Improved network geometry and installation conditions are required for more efficient detection, robust location and improved energetic insights into redd‐building processes in larger reaches. The passive and continuous nature of the seismic approach in detecting redds and describing fish behaviour provides a novel tool for fish biologists and fisheries managers, but also for fluvial geomorphologists, interested in quantifying the amount of sediment mobilized by this ecosystem engineer. When complemented with classic approaches, it could allow for a more holistic picture of the kinetics and temporal patterns (at scales from seconds to multiple seasons) of a key phase of salmonid life cycles. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

Invertebrate zoogeomorphology: A review and conceptual framework for rivers

“…Hassan et al (2008) separated bedload transport due to Salmonidae spawning because this occurred at discharges well below those required for fluvial entrainment of sediment. Seismic signals (Dietze et al, 2020) and the disturbance of markers (Rice et al, 2019), tagged particles (Gottesfeld et al, 2004) and characteristic sediment (De Nadaï‐Monoury et al, 2013) have also been used to measure bioturbation in situ in rivers (for benthic organisms see the review, Maire et al, 2008). Upscaling the effects of biostabilization is more difficult because it requires a measure of how much sediment would have moved in the absence of biology.…”

Do brown trout (Salmo trutta L.) move streambed substrate?—Implications for durability and maintenance of artificial spawning habitat

“…Because the majority of the gravel movement occurred from the central section toward the downstream section, maintenance such as raking gravel from the downstream section to the central section may increase the longevity of gravel patches. While this study represents one of the first to measure sediment transport in artificial spawning habitat, previous work has documented varying degrees of gravel movement for numerous other species in natural spawning habitat (Dietze et al, 2020; Gottesfeld et al, 2004, 2008; Hassan et al, 2008). Also, both mean burial depth and travel distance of tagged tracer substrate have been found to increase with increasing numbers of spawning individuals (Gottesfeld et al, 2004, 2008; Hassan et al, 2008).…”

“…Transport of spawning substrate in streams is, in large part, a result of high water velocities and turbulence during disturbance events such as floods (Gottesfeld, Hassan, Tunnicliffe, & Poirier, 2004; Kondolf, Vick, & Ramirez, 1996; Macdonald, King, & Herunter, 2010), but the extent of sediment transport is also shaped by spawning activities of fish. By excavating streambeds, salmonids move substrate downstream and change the streambed morphology (Dietze et al, 2020; Montgomery, Buffington, Peterson, Schuett‐Hames, & Quinn, 1996). Several studies have concluded sediment transport attributable to spawning salmonids to be comparable with, or even greater than, sediment transport associated with flood events (Gottesfeld, Hassan, & Tunnicliffe, 2008; Hassan et al, 2008).…”

Special issue: German Society for Geomorphology

“…Dietze et al ( 2020 ) quantified, for the first time, the timing, duration and energy transfer of redd building by spawning salmonids using environmental seismological approaches. They employed a small and easy‐to‐handle acoustic sensor network to record the ground motion of sediment agitation along a second‐order stream in the Cascade Mountain Range, NW USA.…”