Pledger_etal_ESPL_2014_accepted.pdf (836.27 kB)

Reduced bed material stability and increased bedload transport caused by foraging fish: a flume study with juvenile Barbel (Barbus barbus)

Download (836.27 kB)
journal contribution
posted on 09.12.2014, 16:36 by Andrew Pledger, Stephen Rice, Jonathan Millett
The plants and animals that inhabit river channels may act as zoogeomorphic agents affecting the nature and rates of sediment recruitment, transport and deposition. The impact of benthic-feeding fish, which disturb bed material sediments during their search for food, has received very little attention, even though benthic feeding species are widespread in rivers and may collectively expend significant amounts of energy foraging across the bed. An ex situ experiment was conducted to investigate the impact of a benthic feeding fish (Barbel Barbus barbus) on particle displacements, bed sediment structures, gravel entrainment and transport fluxes. In a laboratory flume changes in bed surface topography were measured and grain displacements examined when an imbricated, water-worked bed of 5.6 to 16 mm gravels was exposed to feeding juvenile Barbel (on average, 0.195 m in length). Grain entrainment rates and bedload fluxes were measured under a moderate transport regime for substrates that had been exposed to feeding fish and control substrates which had not. On average, approximately 37% of the substrate, by area, was modified by foraging fish during a four-hour treatment period, resulting in increased microtopographic roughness and reduced particle imbrication. Structural changes by fish corresponded with an average increase in bedload flux of 60% under entrainment flows, whilst on average the total number of grains transported during the entrainment phase was 82% higher from substrates that had been disturbed by Barbel. Together, these results indicate that by increasing surface microtopography and undoing the naturally stable structures produced by water working, foraging can increase the mobility of gravel-bed materials. An interesting implication of this result is that by increasing the quantity of available, transportable sediment and lowering entrainment thresholds, benthic feeding might affect bedload fluxes in gravel-bed rivers. The evidence presented here is sufficient to suggest that further investigation of this possibility is warranted

Funding

The authors would like to thank the Barbel Society for providing financial support. AGP was in receipt of a Loughborough University Faculty Studentship.

History

School

  • Social Sciences

Department

  • Geography and Environment

Published in

EARTH SURFACE PROCESSES AND LANDFORMS

Volume

39

Issue

11

Pages

1500 - 1513 (14)

Citation

PLEDGER, A.G., RICE, S.P. and MILLETT, J., 2014. Reduced bed material stability and increased bedload transport caused by foraging fish: a flume study with juvenile Barbel (Barbus barbus). Earth Surface Processes and Landforms, 39 (11), pp. 1500 - 1513.

Publisher

© John Wiley & Sons, Ltd

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2014

Notes

This is the peer reviewed version of the following article: PLEDGER, A.G., RICE, S.P. and MILLETT, J., 2014. Reduced bed material stability and increased bedload transport caused by foraging fish: a flume study with juvenile Barbel (Barbus barbus). Earth Surface Processes and Landforms, 39 (11), pp. 1500 - 1513, which has been published in final form at http://dx.doi.org/10.1002/esp.3592 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

ISSN

0197-9337

Language

en

Exports

Logo branding

Exports