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The importance of seasonal macrophyte cover for the behaviour and performance of brown trout (Salmo trutta) in a groundwater-fed river

The importance of seasonal macrophyte cover for the behaviour and performance of brown trout (Salmo trutta) in a groundwater-fed river
The importance of seasonal macrophyte cover for the behaviour and performance of brown trout (Salmo trutta) in a groundwater-fed river
1. Groundwater-fed rivers, such as the chalk streams of southern England, exhibit high levels of stability (e.g. flow and temperature) and physical homogeneity (e.g. depth and substrate grain size). However, growth of instream macrophytes is highly variable depending on season, providing an important but ever changing source of cover for stream dwelling salmonids, such as brown trout (Salmo trutta). 2. In this study, the behavioural ecology of brown trout inhabiting a chalk stream was assessed during periods that included summer and winter. In a reach of the River Lambourn (Berkshire, UK), a combination of physical habitat mapping, electric-fishing, passive integrated transponder and radio telemetry was used to quantify trout: (1) density relative to physical and thermal characteristics, (2) movement patterns, and (3) performance, in terms of growth. 3. Trout density was positively related to depth during winter (Feb) and spring (May), but not at the end of summer (Sept). Despite no statistical relation between trout density and macrophytes, periods of strong and no association between density and depth coincided with sparse and extensive macrophyte cover throughout the study reach, respectively. 4. Despite being greater for some fish in winter compared to summer, the daily distance moved was generally low (<3.5 m day-1). While growth was mostly positive, less mass was gained, and performance deviated farther from optimal levels predicted by a growth model, during periods that included winter. 5. A number of factors likely contributed to lower growth in winter, including costs of reproduction, temperatures which deviated farther from those optimal for growth, and/or an inability to maximise energy intake, e.g. due to time spent holding position in deeper areas as cover provided by macrophytes declined. 6. Despite the lack of extremes in chalk stream environments, the behavioural ecology of brown trout appears to be influenced by seasonal variation in instream cover provided by macrophytes. This emphasises the importance of balancing the management (e.g. cutting and removal) of macrophytes with the ecological benefits they provide.
chalk stream, habitat complexity, habitat use, instream cover, salmonid
0046-5070
Vowles, Andrew
c35c3a75-2199-4665-8340-e8ee7abc25f4
Kemp, Paul
9e33fba6-cccf-4eb5-965b-b70e72b11cd7
Vowles, Andrew
c35c3a75-2199-4665-8340-e8ee7abc25f4
Kemp, Paul
9e33fba6-cccf-4eb5-965b-b70e72b11cd7

Vowles, Andrew and Kemp, Paul (2019) The importance of seasonal macrophyte cover for the behaviour and performance of brown trout (Salmo trutta) in a groundwater-fed river. Freshwater Biology. (doi:10.1111/fwb.13370).

Record type: Article

Abstract

1. Groundwater-fed rivers, such as the chalk streams of southern England, exhibit high levels of stability (e.g. flow and temperature) and physical homogeneity (e.g. depth and substrate grain size). However, growth of instream macrophytes is highly variable depending on season, providing an important but ever changing source of cover for stream dwelling salmonids, such as brown trout (Salmo trutta). 2. In this study, the behavioural ecology of brown trout inhabiting a chalk stream was assessed during periods that included summer and winter. In a reach of the River Lambourn (Berkshire, UK), a combination of physical habitat mapping, electric-fishing, passive integrated transponder and radio telemetry was used to quantify trout: (1) density relative to physical and thermal characteristics, (2) movement patterns, and (3) performance, in terms of growth. 3. Trout density was positively related to depth during winter (Feb) and spring (May), but not at the end of summer (Sept). Despite no statistical relation between trout density and macrophytes, periods of strong and no association between density and depth coincided with sparse and extensive macrophyte cover throughout the study reach, respectively. 4. Despite being greater for some fish in winter compared to summer, the daily distance moved was generally low (<3.5 m day-1). While growth was mostly positive, less mass was gained, and performance deviated farther from optimal levels predicted by a growth model, during periods that included winter. 5. A number of factors likely contributed to lower growth in winter, including costs of reproduction, temperatures which deviated farther from those optimal for growth, and/or an inability to maximise energy intake, e.g. due to time spent holding position in deeper areas as cover provided by macrophytes declined. 6. Despite the lack of extremes in chalk stream environments, the behavioural ecology of brown trout appears to be influenced by seasonal variation in instream cover provided by macrophytes. This emphasises the importance of balancing the management (e.g. cutting and removal) of macrophytes with the ecological benefits they provide.

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Vowles_Kemp_FB_acceptedMS - Accepted Manuscript
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More information

Accepted/In Press date: 12 June 2019
e-pub ahead of print date: 24 July 2019
Keywords: chalk stream, habitat complexity, habitat use, instream cover, salmonid

Identifiers

Local EPrints ID: 431794
URI: http://eprints.soton.ac.uk/id/eprint/431794
ISSN: 0046-5070
PURE UUID: 8c57d75d-ce7f-4c17-817f-1205c9e26aa0
ORCID for Paul Kemp: ORCID iD orcid.org/0000-0003-4470-0589

Catalogue record

Date deposited: 17 Jun 2019 16:30
Last modified: 07 Oct 2020 05:08

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