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Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles

Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles
Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles
It is commonly assumed that stream-dwelling fish should select positions where they can reduce energetic costs relative to benefits gained and enhance fitness. However, the selection of appropriate hydrodynamic metrics that predict space use is the subject of recent debate and a cause of controversy. This is for three reasons: 1) flow characteristics are often oversimplified, 2) confounding variables are not always controlled, and 3) there is limited understanding of the explanatory mechanisms that underpin the biophysical interactions between fish and their hydrodynamic environment. This study investigated the space use of brown trout, Salmo trutta, in a complex hydrodynamic flow field created using an array of different sized vertically oriented cylinders in a large open-channel flume in which confounding variables were controlled. A hydrodynamic drag function based on single-point time-averaged velocity statistics that incorporates the influence of turbulent fluctuations (D) was used to infer the energetic cost of steady swimming. Novel hydrodynamic preference curves were developed and used to assess the appropriateness of D as a descriptor of space use compared to other commonly used metrics. Zones in which performance enhancing swimming behaviours (e.g. Kármán gaiting, entraining, and bow riding) that enable fish to hold position while reducing energetic costs (termed ‘specialised behaviours’) were identified and occupancy recorded. We demonstrate that energy conservation strategies play a key role in space use in an energetically taxing environment with the majority of trout groups choosing to frequently occupy areas where specialised behaviours may be adopted or by selecting low drag regions.
0022-0949
3480-3491
Kerr, J.R.
cfdf2892-19c2-4206-9416-848b2b0f672c
Manes, C.
7d9d5123-4d1b-4760-beff-d82fe0bd0acf
Kemp, P.S
9e33fba6-cccf-4eb5-965b-b70e72b11cd7
Kerr, J.R.
cfdf2892-19c2-4206-9416-848b2b0f672c
Manes, C.
7d9d5123-4d1b-4760-beff-d82fe0bd0acf
Kemp, P.S
9e33fba6-cccf-4eb5-965b-b70e72b11cd7

Kerr, J.R., Manes, C. and Kemp, P.S (2016) Assessing hydrodynamic space use of brown trout, Salmo trutta, in a complex flow environment: a return to first principles. Journal of Experimental Biology, 219, 3480-3491. (doi:10.1242/jeb.134775). (PMID:27591311)

Record type: Article

Abstract

It is commonly assumed that stream-dwelling fish should select positions where they can reduce energetic costs relative to benefits gained and enhance fitness. However, the selection of appropriate hydrodynamic metrics that predict space use is the subject of recent debate and a cause of controversy. This is for three reasons: 1) flow characteristics are often oversimplified, 2) confounding variables are not always controlled, and 3) there is limited understanding of the explanatory mechanisms that underpin the biophysical interactions between fish and their hydrodynamic environment. This study investigated the space use of brown trout, Salmo trutta, in a complex hydrodynamic flow field created using an array of different sized vertically oriented cylinders in a large open-channel flume in which confounding variables were controlled. A hydrodynamic drag function based on single-point time-averaged velocity statistics that incorporates the influence of turbulent fluctuations (D) was used to infer the energetic cost of steady swimming. Novel hydrodynamic preference curves were developed and used to assess the appropriateness of D as a descriptor of space use compared to other commonly used metrics. Zones in which performance enhancing swimming behaviours (e.g. Kármán gaiting, entraining, and bow riding) that enable fish to hold position while reducing energetic costs (termed ‘specialised behaviours’) were identified and occupancy recorded. We demonstrate that energy conservation strategies play a key role in space use in an energetically taxing environment with the majority of trout groups choosing to frequently occupy areas where specialised behaviours may be adopted or by selecting low drag regions.

Text
Kerr et al., 2016. Assessing hydrodynamic space use of brown trout in a complex flow environment. A return to first principles.pdf - Accepted Manuscript
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More information

Accepted/In Press date: 14 August 2016
e-pub ahead of print date: 2 September 2016
Organisations: Water & Environmental Engineering Group

Identifiers

Local EPrints ID: 399726
URI: https://eprints.soton.ac.uk/id/eprint/399726
ISSN: 0022-0949
PURE UUID: 89a27cde-ba44-4a27-b84e-1c6fc4995ee6
ORCID for J.R. Kerr: ORCID iD orcid.org/0000-0002-2990-7293
ORCID for P.S Kemp: ORCID iD orcid.org/0000-0003-4470-0589

Catalogue record

Date deposited: 25 Aug 2016 10:25
Last modified: 26 Nov 2019 06:34

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